Cross-copolymerized olefin/aromatic vinyl compound/diene copolymer and process for its production

ABSTRACT

A highly uniform vinyl compound polymer-cross-copolymerized olefin/styrene/diene copolymer excellent in processability, mechanical properties, high temperature properties, compatibility and transparency, and its composition and a process for its production, are provided. This copolymer is a crossed polymer obtained by cross-copolymerizing an olefin/styrene/diene copolymer having a styrene content of from 0.03 mol % to 96 mol %, a diene content of from 0.0001 mol % to 3 mol % and the rest being an olefin, with an olefin/aromatic vinyl compound copolymer.

[0001] This is a continuation-in-part application of the applicationSer. No. 09/831,385 having a filing date of May 14, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a novel cross-copolymerizedolefin/aromatic vinyl compound/diene copolymer (hereinafter sometimesabbreviated as a cross-copolymer) and its composition, and furtherprocesses for their production.

[0004] 2. Discussion of Background

[0005] Ethylene/aromatic Vinyl Compound (Styrene) Copolymers

[0006] Some ethylene/aromatic vinyl compound (styrene) random copolymersobtainable by means of a so-called uniform type Ziegler-Natta catalystsystem comprising a transition metal catalyst component and an organicaluminum compound, and processes for their production, are known.

[0007] JP-A-3-163088 and JP-A-7-53618 disclose ethylene/styrenecopolymers having a styrene content of at most 50 mol % and containingno normal (i.e. head-to-tail) styrene chain, so-called pseudo-randomcopolymers, obtainable by means of a complex having a so-calledconstrained geometric structure.

[0008] JP-A-6-49132 and Polymer Preprints, Japan, 42, 2292 (1993)disclose processes for producing similar ethylene/styrene copolymershaving an aromatic vinyl compound content of at most 50 mol % andcontaining no normal aromatic vinyl compound chain, i.e. pseudo-randomcopolymers, by means of a catalyst comprising a crosslinked metallocenetype Zr complex and a cocatalyst. These copolymers have nostereoregularity derived from aromatic vinyl compound units.

[0009] Further, recently, it has been reported to produce anethylene/aromatic vinyl, compound copolymer having a stereoregularity ofalternating copolymerization type by means of a certain specificcrosslinked bisindenyl type Zr complex i.e. aracemic[ethylenebis(indenyl)zirconium dichloride] under an extremely lowtemperature (−25° C.) condition. (Macromol. Chem., Rapid Commun., 17,745 (1996).) However, with the copolymer obtainable by this complex, themolecular weight is not yet practically sufficient, and thecompositional distribution is also large.

[0010] Further, JP-A-9-309925 and JP-A-11-130808 disclose novelethylene/styrene copolymers which respectively have styrene contents offrom 1 to 55 mol % and from 1 to 99 mol % and which haveethylene/styrene alternating structures and isotactic stereoregularityin their styrene chain structures and further have head-to-tail styrenechain structures, with the alternating degrees (λ values in thisspecification) of the copolymers being at most 70. Further, thesecopolymers have high transparency.

[0011] The physical properties of various ethylene/styrene randomcopolymers mentioned above, are strongly influenced by the compositions(the styrene contents) when their molecular weights are sufficientlyhigh. Namely, a copolymer having a relatively low styrene content at alevel of at most 20 mol %, has crystallizability based on thepolyethylene chains, whereby it may have heat resistance at a level offrom 8° C. to 120° C. and further has high mechanical properties.However, if the styrene content becomes higher, the crystallizabilityderived form the polyethylene chains tends to decrease or diminish, andthe heat resistance and mechanical properties tend to decrease. Whenthere is stereoregalarity in ethylene/styrene alternating structures,and relatively many such alternating structures are contained, thecrystallizability derived from such alternating structures will appear,but there may sometimes be a problem with respect to the crystallinityor the crystallization rate. In a copolymer having a high styrenecontent of at least 60 mol %, many isotactic styrene chain structuresare contained, but isotactic styrene chains have a low crystallizationrate, whereby it may lack in practical applicability as a heat resistantresin.

[0012] On the other hand, a copolymer having a low styrene content isexcellent also in cold resistance (embrittle temperature) at a level of−60° C. However, as the styrene content increases, the cold resistancetends, to deteriorate, and in the vicinity of 30 mol %, it will be about−10° C., and in the vicinity of 50 mol %, it will be about roomtemperature.

[0013] A copolymer having a styrene content of from about 15 to 50 mol%, has a feeling, flexibility and stress relaxation property similar topolyvinyl chlorides and is useful as a substitute for polyvinylchlorides. Further, it is excellent in vibration-damping properties andsoundproofing properties. However, its heat resistance and coldresistance are poor, whereby it is hardly useful by itself.

[0014] When used as a stretch film, a copolymer having a styrene contentof from about 30 to 50 mol % shows slow elongation recovery propertiessimilar to a polyvinyl chloride stretch film at room temperature, but ittends to be too stiff under a refrigerating or freezing condition.Further, when it is attempted to produce this film by inflation moldingor extrusion molding with a T-die, the film itself has a high self-tackproperty, and during winding, the film tends to adhere to itself. Aself-tack property to some extent is effective for a substitute for apolyvinyl chloride film, especially as a stretch film for foodpackaging, but it can hardly be compatible with film moldability.

[0015] An ethylene/styrene copolymer having a styrene content of atleast 40 mol % is excellent in printability and tinting property and hasan improved compatibility with a styrene type resin. Especially, acopolymer having a styrene content of at most 20 mol % is inferior inprintability and tinting property, but is excellent in compatibilitywith a polyolefin type resin.

[0016] These random ethylene/styrene copolymers show remarkable changesin the physical properties and compatibility depending upon thecompositions as described above, and they have had a problem that with asingle composition, various properties (such as heat resistance, coldresistance and stress relaxation property or flexibility) can not besatisfied at the same time.

[0017] In order to solve such a problem, it has been proposed to mixethylene/styrene copolymers having different compositions to obtain acomposition (JP-A-2000-129043, WO98/10018), to mix them with polyolefinsto obtain compositions (WO98/10015), or to crosslink them (U.S. Pat. No.5,869,591). However, ethylene/styrene copolymers substantially differentin their compositions have poor compatibility to one another, and theircompositions or compositions with polyolefins tend to be opaque, and themechanical properties may sometimes be impaired, whereby the applicationmay be limited. Further, in the case of crosslinking, there is a problemthat the secondary moldability or recycling property tends to be lost,or the production cost tends to increase.

[0018] Ethylene/α-olefin Copolymers

[0019] Ethylene/α-olefin copolymers, in which 1-hexene, 1-octene or thelike is co-polymerized to ethylene, i.e. so-called LLDPE, are flexibleand transparent and have high strength, whereby they are widely used ase.g. films for general use, packaging materials or containers. However,as a nature of polyolefin type resins, their printability and coatingproperties are low, and special treatment such as corona treatment willbe required for printing or coating. Further, they have poor affinitywith an aromatic vinyl compound polymer such as a polystyrene or a polarpolymer, and in order to obtain a composition with such a resin havinggood mechanical properties, it has been necessary to employ an expensivecompatibilizing agent additionally.

[0020] Common Graft Copolymers

[0021] As a method for obtaining a graft copolymer, a method has beenheretofore known wherein a graft copolymer of an olefin type polymer oran olefin/styrene type copolymer is obtained during the polymerizationor during the mold processing by a common known radical graft treatment.However, by this method, it has been difficult to obtain high graftefficiency, and the method is disadvantageous from the viewpoint ofcosts. Further, the obtainable graft copolymer usually has a problemthat it is non-uniform and partially gelled to be not melting, wherebythe moldability tends to be impaired. The graft copolymer thus obtained,usually has graft chains independently branched from the polymer mainchain, but when such copolymer is employed as a composition or acompatibilizing agent, the strength of the interface of the polymermicrostructure can not be said to be sufficient.

SUMMARY OF THE INVENTION

[0022] The present invention is firstly to solve the foregoing problemsof the prior art and to provide a cross-copolymerized olefin/aromaticvinyl compound/diene copolymer which satisfies heat resistance andvarious mechanical properties, processability, compatibility andtransparency, and its composition and an industrially excellent processfor producing such a cross-copolymer.

[0023] The present invention is secondly to provide as applications ofthe cross-copolymer of the present invention, various resin compositionsor molded products containing the cross-copolymer, which have theabove-mentioned problems of various resin compositions or moldedproducts solved or improved.

DISCLOSURE OF THE INVENTION

[0024] Cross-copolymerized Olefin/aromatic Vinyl Compound/dieneCopolymer (a Cross-copolymer)

[0025] In this specification, an aromatic vinyl compound content of acopolymer represents a content of units derived from an aromatic vinylcompound monomer, contained in the copolymer. An olefin content and adiene content likewise represent contents of the respective monomerunits.

[0026] The cross-copolymer of the present invention is across-copolymerized olefin/aromatic vinyl compound/diene copolymercharacterized in that it is obtained by cross-copolymerizing anolefin/aromatic vinyl compound/diene copolymer having an aromatic vinylcompound content of from 0.03 mol % to 96 mol %, a diene content of from0.0001 mol % to 3 mol % and the rest being an olefin, with anolefin/aromatic vinyl compound copolymer (which may contain a diene)having an aromatic vinyl compound content which is different by at least5 mol %.

[0027] Further, the cross-copolymer of the present invention is acopolymer (which will be referred to as a cross-copolymerizedolefin/aromatic vinyl compound/diene copolymer or simply as across-copolymer) obtained by synthesizing an olefin/aromatic vinylcompound/diene copolymer having an aromatic vinyl compound content offrom 0.03 mol % to 96 mol %, a diene content of from 0.0001 mol % to 3mol % and the rest being an olefin (main chain), followed bycross-copolymerizing an olefin/aromatic vinyl compound copolymer havingan aromatic vinyl compound content of from 0 mol % to 96 mol % and therest being an olefin, preferably an aromatic vinyl compound content offrom 0.03 mol % to 96 mol % and the rest being an olefin, wherein thearomatic vinyl compound content is different by at least 5 mol %.

[0028] Further, the cross-copolymer of the present invention is across-copolymerized olefin/aromatic vinyl compound/diene copolymercharacterized in that it is obtained, by using an olefin/aromatic vinylcompound/diene copolymer having an aromatic vinyl compound content offrom 0.03 mol % to 96 mol %, a diene content of from 0.0001 mol % to 3mol % and the rest being an olefin, and cross-copolymerizing it, whereinthe aromatic vinyl compound content is different by at least 2 mol % ascompared with the olefin/aromatic vinyl compound/diene copolymer priorto the cross-copolymerization.

[0029] Further, preferably, the cross-copolymer of the present inventionis a cross-copolymerized olefin/aromatic vinyl compound/diene copolymercharacterized in that it is obtained by cross-copolymerizing anolefin/aromatic vinyl compound/diene copolymer having an aromatic vinylcompound content of from 0.03 mol % to 96 mol %, a diene content of from0.0001 mol % to 3 mol % and the rest being an olefin, with an olefin(co)polymer or an olefin/aromatic vinyl compound copolymer (which maycontain a diene), wherein the aromatic vinyl compound content isdifferent by at least 2 mol %, preferably at least 5 mol %, as comparedwith an olefin/aromatic vinyl compound/diene copolymer prior to thecross-copolymerization.

[0030] The cross-copolymer of the present invention may finally have acomposition such that the aromatic vinyl compound content is from 0.03mol % to 96 mol %, the diene content is from 0.0001 mol % to 3 mol %,and the rest being an olefin, preferably a composition such that thearomatic vinyl compound content is from 5 mol % to 96 mol %, the dienecontent is from 0.0001 mol % to 3 mol %, and the rest being an olefin.

[0031] The weight average molecular weight of the cross-copolymer of thepresent invention is at least 10,000, preferably at least 30,000,particularly preferably at least 60,000, and at most 1,000,000,preferably at most 500,000. The molecular weigh distribution (Mw/Mn) isnot particularly limited, but is usually at most 10, preferably at most7, most preferably at most 5, and at least 1.5.

[0032] Further, in the specification of the present invention, thecross-copolymer is a polymer which can directly be obtained by theprocess of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a schematic view illustrating the cross-copolymer of thepresent invention.

[0034]FIG. 2 is a schematic view illustrating a conventional graftedcopolymer.

[0035]FIG. 3 is a graph showing the relation between the melting pointsand the compositions of cross-copolymers of Examples 1 to 3 of thepresent invention and ethylene/styrene copolymers.

[0036]FIG. 4 is a graph showing the relation between the Vicat softeningpoints and the compositions of cross-copolymers of the presentinvention, ethylene/styrene copolymers and blends of ethylene/styrenecopolymers.

[0037]FIG. 5 shows an X-ray diffraction diagram and a multiple peakseparation results of a cross-copolymer of the present invention.

[0038]FIG. 6 is an X-ray diffraction diagram and a multiple peakseparation result of an ethylene/styrene copolymer.

[0039]FIG. 7 is a viscoelasticity spectrum of cross-copolymer (1-C).

[0040]FIG. 8 is a viscoelasticity spectrum of cross-copolymer (2-C).

[0041]FIG. 9 is a viscoelasticity spectrum of an ethylene/styrenecopolymer having a styrene content of 11 mol %.

[0042]FIG. 10 is a graph showing the relation between the melting pointsand the compositions of cross-copolymers of Examples 8 to 13 of thepresent invention and ethylene/styrene copolymers.

[0043]FIG. 11 is a transmission electron microscopic (TEM) photograph ofa cross-copolymer.

[0044]FIG. 12 is a TEM photograph of an ethylene/styrene copolymercomposition of Comparative Example 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Further, the present invention is a cross-copolymer constitutedpreferably by the structure shown in FIG. 1 or comprising the structureshown in FIG. 1.

[0046] Namely, as shown in FIG. 1, it is a copolymer having mainly astructure in which a main chain olefin/aromatic vinyl compound/dienecopolymer is bonded (cross-bonded or intersectingly bonded) with crosschains, at one point or plural points, via diene units. Such across-structure may be rephrased as a star structure. Further, in theclassification by the POLY division of the American Chemical Society, itis called a segregated star copolymer (Polymer Preprints, 1998, March).In the description of the present invention, the olefin/aromatic vinylcompound copolymer or olefin (co)polymer cross-bonded to the main chainolefin/aromatic vinyl compound/diene copolymer will be referred to as across chain.

[0047] Whereas as shown in FIG. 2, a graft copolymer known to thoseskilled in the art is a copolymer having mainly polymer chains branchedfrom one point or plural points of the main chain.

[0048] With a structure such that a polymer main chain is cross-bonded(intersectingly bonded) with other polymer chains (which may be calledalso as a star structure), when it is employed as a composition orcompatibilizing agent, it is usually believed to show superior strengthof the interface of the polymer microstructure and present highmechanical properties, as compared with a grafted structure.

[0049] Preferably, the cross-copolymer of the present invention hascharacteristics such that at least one melting point by DSC is observedat a level of from 80° C. to 1400° C., preferably from 95° C. to 140°C., and its heat of crystal fusion is at least 10 J/g and at most 150J/g, preferably at least 20 J/g and at most 120 J/g. The crystalstructure to give such heat of crystal fusion is preferably a crystalstructure based on an ethylene chain structure. This crystal structurecan be ascertained by a known method such as an X-ray diffractionmethod.

[0050] Further, the cross-copolymer of the present invention is across-copolymerized olefin/aromatic vinyl compound/diene copolymer,characterized in that it has an aromatic vinyl compound content of from5 mol % to 50 mol %, a diene content of from 0.0001 mol % to 3 mol % andthe rest being ethylene or at least two types of olefins includingethylene, and it has a crystal structure derived from an ethylene chainstructure, wherein the aromatic vinyl compound content and at least oneof the melting point such that the heat of crystal fusion as measured byDSC is at least 10 J/g and at most 150 J/g, satisfies the followingrelation:

(5≦St≦15)

−3·St+125≦Tm≦140

(15<St≦50)

80<Tm≦140

[0051] where Tm is the melting point (° C.) such that the heat ofcrystal fusion is at least 10 J/g and at most 150 J/g, and St is thearomatic vinyl compound content (mol %).

[0052] Further preferably, the cross-copolymer of the present inventionis a cross-copolymerized olefin/aromatic vinyl compound/diene copolymer,characterized in that it has an aromatic vinyl compound content of from5 mol % to 15 mol %, a diene content of from 0.0001 mol % to 3 mol % andthe rest being ethylene or at least two types of olefins includingethylene, wherein the aromatic vinyl compound content and the meltingpoint such that the heat of crystal fusion as measured by DSC is atleast 10 J/g and at most 150 J/g, satisfy the following relation:

(5≦St≦10)

−3·St+125≦Tm≦140

(10<St≦15)

95≦Tm≦140

[0053] where Tm is the melting point (° C.) such that the heat ofcrystal fusion is at least 10 J/g and at most 150 J/g, and St is thearomatic vinyl compound content (mol %).

[0054] Further preferably, it is a cross-copolymerized olefin/aromaticvinyl compound/diene copolymer which has a single melting point asobserved by DSC and the melting point of which satisfies theabove-mentioned relation.

[0055] Further, the cross-copolymer of the present invention is across-copolymerized olefin/aromatic vinyl compound/diene copolymer,characterized in that it has an aromatic vinyl compound content of from5 mol % to 20 mol %, a diene content of from 0.0001 mol % to 3 mol % andthe rest being ethylene of at least two types of olefins includingethylene, wherein the aromatic vinyl compound content, and the Vicatsoftening point satisfy the following relation:

(5≦St≦20)

−3·St+120≦T vicat≦140

[0056] where T vicat is the Vicat softening point (° C.), and St is thearomatic vinyl compound content (mol %).

[0057] Further preferably, it is a cross-copolymerized olefin/aromaticvinyl compound/diene copolymer, characterized in that it has an aromaticvinyl compound content of from 5 mol % to 15 mol %, a diene content offrom 0.0001 mol % to 3 mol % and the rest being ethylene or at least twotypes of olefins including ethylene, wherein the aromatic vinyl compoundcontent and the Vicat softening point satisfy the following relation:

(5≦St≦15)

−3·St+120≦T vicat≦140

[0058] where T vicat is the Vicat softening point (° C.), and St is thearomatic vinyl compound content (mol %).

[0059] Among cross-copolymers of the present invention, across-copolymerized ethylene/styrene/divinylbenzene copolymer can haveat least one glass transition point within a range of from −30° C. to−15° C. The glass transition point is a glass transition point obtainedby a tangent method (on set method) in the DSC measurement.

[0060] In a molded sheet product of 1 mm, the cross-copolymerizedolefin/aromatic vinyl compound/diene copolymer of the present invention,may have a haze of at most 30%, preferably at most 20%.

[0061] In a heat molded product of 1 mm, the cross-copolymerizedolefin/aromatic vinyl compound/diene copolymer of the present inventionmay have a total light transmittance of at least 70%, preferably atleast 80%.

[0062] Further, the present invention is a cross-copolymerizedolefin/aromatic vinyl compound/diene compound excellent inprocessability, of which MFR as measured under a load of 5 kg at 200° C.is at least 0.02 g/10 min., preferably at least 0.2 g/10 min. and atmost 100 g/10 min., more preferably MFR as measured under a load of 5 kgat 230° C. is at least 1.0 g/10 min. and at most 50 g/10 min.

[0063] Further, the present invention is a cross-copolymerizedolefin/aromatic vinyl compound/diene copolymer containing a small gelcontent or substantially no gel content, whereby the boiling xyleneinsoluble (the gel content) obtained by ASTM D-2765-84 is less than 10weight %, preferably less than 1 weight %, most preferably, less than0.1 weight %, of the entirety.

[0064] The present invention is preferably a cross-copolymerizedolefin/aromatic vinyl compound/diene copolymer, wherein the olefin isethylene or at least two types of olefins including ethylene.

[0065] Further, the cross-copolymer of the present invention is acopolymer which can be obtained by the following process.

[0066] The cross-copolymer of the present invention includes not only aconcept representing the cross-copolymer itself but also a concept of acomposition containing the cross-copolymer and an olefin/aromatic vinylcompound copolymer not-crossed, which is obtainable in the firstpolymerization step and the second or subsequent polymerization step(which may sometimes be hereinafter referred to as a secondpolymerization step) at an optional ratio. Such a composition containinga cross-copolymer can be obtained by the process of the presentinvention.

[0067] The cross-copolymer of the present invention has differentcontents of vinyl aromatic compound in the main chain and in the crosschains, so that if it contains olefin/aromatic vinyl compound copolymerswith different compositions (aromatic vinyl compound contents), whichare obtainable in the respective polymerization steps, it is believed tohave a function as a compatibilizing agent for them. Therefore, thecross-copolymer obtainable by the process of the present invention, isconsidered to have excellent mechanical properties, high heatresistance, transparency and processability, as compared with usualolefin/aromatic vinyl compound copolymers.

[0068] Further, the present invention provides an economically excellentprocess for producing a cross-copolymerized olefin/aromatic vinylcompound/diene copolymer and provides a cross-copolymerizedolefin/aromatic vinyl compound/diene copolymer thereby obtainable. Sucha cross-copolymer is very useful in a wide range of applications.

[0069] Process for Producing a Cross-copolymerized Olefin/aromatic VinylCompound/diene Copolymer

[0070] The present invention is a cross-copolymerized olefin/aromaticvinyl compound/diene copolymer (a cross-copolymer) which can be obtainedby the following process. Further, the process for producing across-copolymer is capable of producing a cross-copolymer which isuniform and which has good processability and excellent transparency andmechanical properties with efficiency and economical feasibilitysuitable for industrial application.

[0071] Namely, the present invention is a process for producing across-copolymer, which comprises, as a first polymerization step (a mainchain polymerization step), carrying out copolymerization of an aromaticvinyl compound monomer, an olefin monomer and a diene monomer by meansof a coordination polymerization catalyst to synthesize anolefin/aromatic vinyl compound/diene copolymer, and then, as a secondpolymerization step (a crossing step), cross-copolymerizing anolefin/aromatic vinyl compound copolymer using such a copolymer, anolefin, an aromatic vinyl compound monomer and a coordinationpolymerization catalyst. This process is a process employing at leasttwo polymerization steps comprising the above first polymerization step(the main polymerization step) and the second polymerization step (thecrossing step).

[0072] It is necessary that the aromatic vinyl compound content of theolefin/aromatic vinyl compound/diene copolymer to be polymerized in thefirst polymerization step (the main chain polymerization step) and theaverage aromatic vinyl compound content of an olefin/aromatic vinylcompound copolymer to be polymerized in the second or subsequentpolymerization step (which may sometimes be hereinafter referred to as asecond polymerization step) (when the polymerization solution obtainedin the first polymerization step, is used itself in the secondpolymerization step, the polymer thereby obtainable contains a smallamount of a residual diene copolymerized) are different by at least 5mol %, preferably at least 10 mol %, most preferably at least 15 mol %.The aromatic vinyl compound content of an olefin/aromatic vinyl compoundcopolymer to be polymerized in the second or subsequent polymerizationstep (the crossing step) may be 0% in an extreme case. In such a case,an olefin polymer containing no aromatic vinyl compound will be crosschains.

[0073] Further, it is necessary that the aromatic vinyl compound contentof the olefin/aromatic vinyl compound/diene copolymer in the firstpolymerization step and the aromatic vinyl compound content of thefinally obtainable cross-copolymerized olefin/aromatic vinylcompound/diene copolymer are different by at least 2 mol %, preferablyat least 5 mol %, more preferably at least 10 mol %.

[0074] First Polymerization Step (Main Chain Polymerization Step)

[0075] The olefin/aromatic vinyl compound/diene copolymer to be used inthe present invention, can be obtained by copolymerizing an aromaticvinyl compound monomer, an olefin monomer and a diene monomer in thepresence of a single site coordination polymerization catalyst.

[0076] The olefin to be used in the present invention may, for example,be ethylene or a C₃₋₂₀ α-olefin, such as propylene, 1-butene, 1-hexene,4-methyl-1-pentene or 1-octene, or a cyclic olefin such as cyclopenteneor norbornene. Preferably, a mixture of ethylene with an α-olefin suchas propylene, 1-butene, 1-hexene or 1-octene, an α-olefin such aspropylene, or ethylene, is employed. More preferably ethylene or amixture of ethylene with an α-olefin, is employed. Particularlypreferably, ethylene is employed.

[0077] As the aromatic vinyl compound to be used in the presentinvention, styrene is preferably employed, but it is possible to employother aromatic vinyl compound, such as p-chlorostyrene,p-tert-butylstyrene, vinyl naphthalene, p-methylstyrene, vinylnaphthalene or vinyl anthracene. Further, a mixture of such compoundsmay be employed.

[0078] Further, as the diene to be used in the present invention, acoordination-polymerizable diene may be employed. Preferably,1,4-hexadiene, 1,5-hexadiene, ethylidenenorbornene, dicyclopentadiene,norbornadiene, 4-vinyl-1-cyclohexene, 3-vinyl-1-cyclohexene,2-vinyl-1-cyclohexene-, o-divinylbenzene, p-divinylbenzene,m-divinylbenzene, or a mixture of them, may be mentioned. Further, it ispossible to employ a diene wherein a plurality of double bonds (vinylgroups) are bonded via a C₆₋₃₀ hydrocarbon group containing a single orplural aromatic vinyl ring structures. Further, dienes disclosed inJP-A-6-136060 and JP-A-11-124420 can also be employed in the presentinvention. Preferred is a diene wherein one of double bonds (vinylgroups) is used for coordination polymerization so that remaining doublebonds in a polymerized state are coordination-polymerizable. Morepreferably, one of o-, p- and m-divinylbenzenes, or a mixture thereof,is suitably employed. Most preferably, m-divinylbenzene having an isomerpurity of at least 80 weight %, preferably at least 90 weight %, isemployed.

[0079] In the present invention, the amount of the diene to be used inthe main chain polymerization step is from 1/50,000 to 1/100, preferablyfrom 1/20,000 to 1/400, of the amount of styrene to be used, in a molarratio. If the main chain polymerization step is carried out at a dieneconcentration higher than this, many crosslinking structures of polymerwill be formed during the polymerization, whereby gelation or the likewill take place, or the processability or physical properties of thecross-copolymer finally obtainable via the crossing step, tend todeteriorate, such being undesirable. Further, if the main chainpolymerization step is carried out at a diene concentration higher thanthis, the residual diene concentration in the polymerization solutiontends to be high, and if such a polymer solution is used for thecrossing step as it is, many crosslinking structures tend to form,whereby the obtained cross-copolymer tends to be likewise poor in theprocessability or physical properties.

[0080] In order to obtain a cross-copolymer excellent particularly insoftness, the olefin/aromatic vinyl compound/diene copolymer polymerizedin the first polymerization step (the main chain polymerization step),preferably has a composition wherein the aromatic vinyl compound contentis at least about 15 mol % and at most 50 mol %, the diene content is atleast 0.001 mol % and less than 0.5 mol %, and the rest is an olefin.Particularly, in order to obtain a cross-copolymer having thecharacteristics of a soft polyvinyl chloride resin (a feeling such assoftness, a tan δ component in the vicinity of room temperature in theviscoelasticity spectrum), the aromatic vinyl compound is particularlypreferably styrene, and in such a case, an olefin/aromatic vinylcompound/diene copolymer having a styrene content of from about 20 mol %to 50 mol %, a diene content of from 0.001 mol % to less than 0.5 mol %and the rest being an olefin, is employed.

[0081] Further, in order to obtain a cross-copolymer having bothsoftness and cold resistance, the olefin/aromatic vinyl compound/dienecopolymer polymerized in the first polymerization step (the main chainpolymerization step), preferably has a composition wherein the aromaticvinyl compound content is at least 10 mol % and at most 30 mol %, thediene content is at least 0.001 mol % and less than 0.5 mol %, and therest is an olefin.

[0082] Further, the diene content of the olefin/aromatic vinylcompound/diene copolymer obtained in the first polymerization step (themain chain polymerization step) is at least 0.0001 mol % and at most 3mol %, preferably at least 0.001 mol % and less than 0.5 mol %, mostpreferably at least 0.01 mol % and less than 0.3 mol %. If the dienecontent in the copolymer is higher, the processability of thecross-copolymer finally obtainable via the second polymerization step(the crossing step) tends to be poor, such being undesirable.

[0083] The single site coordination polymerization catalyst to be usedin the first polymerization step (the main chain polymerization step)may, for example, be a polymerization catalyst comprising a transitionmetal compound and a cocatalyst i.e. a soluble Zieglar-Natta catalyst ora transition metal compound catalyst activated with methyl aluminoxaneor a boron compound (a so-called metallocene catalyst or halfmetallocene catalyst, a CGCT catalyst, etc.).

[0084] Specifically, polymerization catalysts disclosed in the followingliteratures and patents, can be employed.

[0085] For example, metallocene catalysts disclosed in U.S. Pat. No.5,324,800, JP-A-7-37488, JP-A-6-49132, Polymer Preprints, Japan, 42,2292 (1993), Macromol. Chem., Rapid Commun., 17, 745 (1996),JP-A-9-309925, EP0872492A2 and JP-A-6-184179.

[0086] Half metallocene catalysts disclosed in Makromol. Chem. 191, 2387(1990).

[0087] CGCT catalysts disclosed in JP-A-3-163088, JP-A-7-53618 and EP-A416815.

[0088] Soluble Zieglar-Natta catalysts disclosed in JP-A-3-250007 andStud. Surf. Sci. Catal, 517 (1990).

[0089] An olefin/aromatic vinyl compound/diene copolymer having auniform composition with a diene uniformly contained in the polymer, issuitably employed to obtain a cross-copolymer of the present invention.However, it is difficult to obtain such a copolymer having a uniformcomposition by Zieglar-Natta catalyst, and a single site coordinationpolymerization catalyst is preferably employed. The single sitecoordination polymerization catalyst is a polymerization catalystcomprising a transition metal compound and a cocatalyst, i.e. apolymerization catalyst comprising a transition metal compound catalystactivated with methyl aluminoxane or a boron compound (a so-calledmetallocene catalyst or half metallocene catalyst, a CGCT catalyst,etc.).

[0090] In the present invention, a single site coordinationpolymerization catalyst comprising one type of a transition metalcompound and a cocatalyst, is preferably employed.

[0091] In the present invention, the single site coordinationpolymerization catalyst to be most preferably employed, is apolymerization catalyst comprising a transition metal compoundrepresented by the following general formula (1) and a cocatalyst.

[0092] When a polymerization catalyst comprising a transition metalcompound represented by the following general formula (1) and acocatalyst, is employed, a diene, particularly divinylbenzene, can becopolymerized to a polymer in high efficiency, whereby it is possible tosubstantially reduce the amount of the diene to be employed in the firstpolymerization step (the main chain polymerization step) and the amountof an unreacted diene remaining in the polymerization solution.

[0093] If the amount of the diene to be employed in the main chainpolymerization step is large, i.e. if the concentration is high,crosslinking of the polymer takes place substantially as the diene unitstructures serve as crosslinking points during the main chainpolymerization, whereby gelation or non-solubilization takes place, andthe cross-copolymer or the processability of the cross-copolymer tendsto deteriorate. Further, if the non-polymerized diene remainssubstantially in the polymerization solution obtained in the main chainpolymerization step, the crosslinking degree of cross chains will beremarkably high in the subsequent cross polymerization step, whereby theobtained crossed copolymer or the cross-copolymer will be insolubilizedor gelled to deteriorate the processability.

[0094] Further, when a polymerization catalyst comprising a transitionmetal compound represented by the following general formula (1) and acocatalyst, is employed, it is possible to produce an olefin/aromaticvinyl compound/diene copolymer having a uniform composition with aremarkably high activity suitable for industrial application. Further, acopolymer having high transparency can be presented especially with acopolymer having an aromatic vinyl compound content of from 1 mol % to20 mol %. Further, with a composition having an aromatic vinyl compoundcontent of from 1 mol % to 96 mol %, an olefin/aromatic vinylcompound/diene copolymer excellent in mechanical properties, having anisotactic stereoregularity and a head-to-tail styrene chain structure,can be presented.

[0095] wherein A and B are independently a group selected from anunsubstituted or substituted benzoindenyl group, an unsubstituted orsubstituted cyclopentadienyl group, an unsubstituted or substitutedindenyl group, or an unsubstituted or substituted fluorenyl group;

[0096] Y is a methylene group, a silylene group, an ethylene group, agermilene group or a boron residue, which has bonds to A and B and whichfurther has hydrogen or a group containing a C₁₋₂₀ hydrocarbon (thisgroup may have from 1 to 5 nitrogen, boron, silicon, phosphorus,selenium, oxygen, fluorine, chlorine or sulfur atoms), as a substituent,the substituents may be the same or different from one another, and Ymay have a cyclic structure such as a cyclohexylidene group or acyclopeontylidene group;

[0097] each X is independently hydrogen, a halogen, a C₁₋₁₅ alkyl group,a C₆₋₁₀ aryl group, a C₈₋₁₂ alkylaryl group, a silyl group having a C₁₋₄hydrocarbon substituent, a C₁₋₁₀ alkoxy group, or an amide group havinghydrogen or a C₁₋₂₂ hydrocarbon substituent, and n is an integer of 0, 1or 2; and

[0098] M is zirconium, hafnium or titanium,

[0099] Particularly preferred is a polymerization catalyst comprising atransition metal compound of the above general formula (1), wherein atleast one of A and B is an unsubstituted or substituted benzoindenylgroup or an unsubstituted or substituted indenyl group, and acocatalyst.

[0100] The unsubstituted or substituted benzoindenyl group can berepresented by the following formulae Ka 3 to Ka 5. In the followingchemical formulae, each of R1b to R3b which are independent of oneanother, is hydrogen, a C₁₋₂₀ hydrocarbon group which may contain from 1to 3 nitrogen, boron, silicon, phosphorus, selenium, oxygen or sulfuratoms, preferably a C₁₋₂₀ alkyl group, a C6-10 aryl group or a C₇₋₂₀alkylaryl group, or a halogen atom, an OSiR₃ group, a SiR₃ group, a NR₂group or a PR₂ group (each R represents a C₁₋₁₀ hydrocarbon group).Further, adjacent such groups may together form a single or plural 5- to10-membered aromatic or alicyclic rings.

[0101] Further, each of R1a to R3a which are independent of one another,is hydrogen, a C₁₋₂₀ hydrocarbon group which may contain from 1 to 3nitrogen, boron, silicon, phosphorus, selenium, oxygen or sulfur atoms,preferably a C₁₋₂₀ alkyl group, a C₆₋₁₀ aryl group or a C₇₋₂₀ alkylarylgroup, or a halogen atom, an OSiR₃ group, a SiR₃ group, NR₂ group or aPR₂ group (each R represents a C₁₋₁₀ hydrocarbon group), but ispreferably hydrogen.

[0102] The unsubstituted benzoindenyl group may, for example, be4,5-benzo-1-indenyl (another name: benzo(e)indenyl), 5,6-benzo-1-indenylor 6,7-benzo-1-indenyl, and the substituted benzoindenyl group, may, forexample, be α-acenaphtho-1-indenyl, 3-cyclopenta[c]phenanthryl, or1-cyclopenta[1]phenanthryl.

[0103] Particularly preferably, the unsubstituted benzoindenyl group is4,5-benzo-1-indenyl (another name: benzo(e)indenyl), and the substitutedbenzoindenyl may, for example, be α-acenaphtho-1-indenyl,3-cyclopenta[c]phenanthryl or 1-cyclopenta[1]phenanthryl.

[0104] The unsubstituted or substituted indenyl group, the unsubstitutedor substituted fluorenyl group, or the unsubstituted or substitutedcyclopentadienyl group may be represented by the formulae Ka 6 to Ka 8.

[0105] Each of R4band R6 which are independent of each other ishydrogen, a C₁₋₂₀ hydrocarbon group which may contain from 1 to 3nitrogen, boron, silicon, phosphorus, selenium, oxygen or sulfur atoms,preferably a C₁₋₂₀ alkyl group, a C₆₋₁₀ aryl group or a C₇₋₂₀ alkylarylgroup, or a halogen atom, an OSiR₃ group, a SiR₃ group, a NR₂ group or aPR₂ group (each R represents a C₁₋₁₀ hydrocarbon group). Further,adjacent such groups may together form a single or plural 5- to10-membered (except for 6-membered) aromatic or alicyclic rings.However, preferred is hydrogen.

[0106] Each R5 is independently hydrogen, a C₁₋₂₀ hydrocarbon groupwhich may contain from 1 to 3 nitrogen, boron, silicon, phosphorus,selenium, oxygen or sulfur atoms, preferably a C₁₋₂₀ alkyl group, aC₆₋₁₀ aryl group, or a C₇₋₂₀ alkylaryl group, or a halogen atom, anOSiR₃ group, a SiR₃ group, a NR₂ group or a PR₂ group (each R representsa C₁₋₁₀ hydrocarbon group). Further, adjacent such groups may togetherform a single or plural 5- to 10-membered aromatic or alicyclic rings.However, preferred is hydrogen.

[0107] Further, R₄a is independently hydrogen, a C₁₋₂₀ hydrocarbon groupwhich may contain from 1 to 3 nitrogen, boron, silicon, phosphorus,selenium, oxygen or sulfur atoms, preferably a C₁₋₂₀ alkyl group, aC₆₋₁₀ aryl group or a C₇₋₂₀ alkylaryl group, or a halogen atom, an OSiR₃group, a SiR₃ group, a NR₂ group or a PR₂ group (each R represents aC₁₋₁₀ hydrocarbon group), but is preferably hydrogen.

[0108] When both A and B are an unsubstituted or substitutedbenzoindenyl group, or an unsubstituted or substituted indenyl group,they may be the same or different.

[0109] For the production of a copolymer to be used in the presentinvention, it is particularly preferred that at least one of A and B isan unsubstituted or substituted benzoindenyl group.

[0110] Further, it is most preferred that both are an unsubstituted orsubstituted benzoindenyl group.

[0111] In the above general formula (1), Y is a methylene group, asilylene group, an ethylene group, a germilene group or a boron residue,which has bonds to A and B and which further has hydrogen or a groupcontaining a C₁₋₂₀ hydrocarbon (this group may have from 1 to 5nitrogen, boron, silicon, phosphorus, selenium, oxygen, fluorine,chlorine or sulfur atoms), as a substituent. The substituents may be thesame or different from one another. Further, Y may have a cyclicstructure such as a cyclohexylidene group or a cyclopentylidene group.

[0112] Preferably, Y is a substituted methylene group or a substitutedboron group, which has bonds to A and B and which is substituted byhydrogen, a C₁₋₂₀ hydrocarbon group, an amino group or a trimethylsilylgroup. More preferably, Y is a substituted methylene group, which hasbonds to A and B and which is substituted by hydrogen or a C₁₋₂₀hydrocarbon group.

[0113] The hydrocarbon group may, for example, be an alkyl group, anaryl group, a cycloalkyl group or a cycloaryl group. The substituentsmay be the same or different from one another.

[0114] As preferred examples, Y is, for example, —CH₂—, —CMe₂—, —CEt₂—,—CPh₂—, a cyclohexylidene group or a cyclopentylidene group. Here, Merepresents a methyl group, Et an ethyl group, and Ph a phenyl group.

[0115] Each X is independently hydrogen, a halogen, a C₁₋₁₅ alkyl group,a C₆₋₁₀ aryl group, a C₈₋₁₀ alkylaryl group, a silyl group having a C₁₋₄hydrocarbon substituent, a C₁₋₁₀ alkoxy group, or an amide group or anamino group, which has hydrogen or a C₁₋₂₂ hydrocarbon substituent, andn is an integer of 0, 1 or 2.

[0116] The halogen may be chlorine, bromine or fluorine, the alkyl groupmay, for example, be a methyl group or an ethyl group, the aryl groupmay, for example, be a phenyl group, the alkylaryl group may, forexample, be a benzyl group, the silyl group may, for example, be atrimethylsilyl group, the alkoxy group may, for example, be a methoxygroup, an ethoxy group or an isopropoxy group, and the amide group may,for example, be a dialkylamide group such as a dimethylamide group, oran aryl amide group such as N-methyl anilide, N-phenyl anilide or ananilide group. Further, as X, the groups disclosed in U.S. Pat. No.5,859,276 and U.S. Pat. No. 5,892,075 may be employed.

[0117] M is zirconium, hafnium or titanium, particularly preferablyzirconium.

[0118] As examples of such a transition metal compound, the transitionmetal compounds disclosed in EP-0872492A2, JP-A-11-130808,JP-A-9-309925, WO00/20426, EP-0985689A2 and JP-A-6-184179, may bementioned.

[0119] Particularly preferred are transition metal compounds having asubstituted methylene-bridged structure, as specifically disclosed inEP-0872492A2, JP-A-11-130808 and JP-A-9-309925.

[0120] As the cocatalyst to be used in the process of the presentinvention, a known cocatalyst used in combination is with a conventionaltransition metal compound, or an alkyl aluminum compound may be used. Assuch a cocatalyst, methyl aluminoxane (or may be referred to as methylalumoxane or MAO) or a boron compound is suitably employed. As examplesof the cocatalyst (methyl aluminoxane or a boron compound) or the alkylaluminum compound to be used, the cocatalysts (methyl aluminoxane orboron compounds) or the alkyl aluminum compounds disclosed inEP-0872492A2, JP-A-11-130808, JP-A-9-309925, WO00/20426, EP-0985689A2 orJP-A-6-184179, may be mentioned.

[0121] Further, the cocatalyst to be used at that time, is preferably analuminoxane (or may be referred to as an alumoxane) represented by thefollowing general formula (2) or (3).

[0122] wherein R is a C₁₋₅ alkyl group, a C₆₋₁₀ aryl group or hydrogen,and m is an integer of from 2 to 100. The plurality of R may be the sameor different from one another.

[0123] wherein R′ is a C₁₋₅ alkyl group, a C₆₋₁₀ aryl group or hydrogen,and n is an integer of from 2 to 100. The plurality of R′ may be thesame or different from one another.

[0124] At the time of producing an olefin/aromatic vinyl compound/dienecopolymer to be used in the present invention, the above describedvarious monomers, the transition metal compound (the metal complex) andthe cocatalyst are brought in contact with one another. With respect tothe order of contact and the contacting method, optional known methodsmay be employed.

[0125] The above copolymerization or polymerization method may, forexample, be a method of polymerizing in a liquid monomer without using asolvent, or a method of employing a single solvent or a mixed solventselected from a saturated aliphatic or aromatic hydrocarbon or ahalogenated hydrocarbon, such as pentane, hexane, heptane, cyclohexane,benzene, toluene, ethylbenzene, xylene, chloro-substituted benzene,chloro-substituted toluene, methylene chloride or chloroform.Preferably, a mixed alkane type solvent, cyclohexane, toluene orethylbenzene is employed. The polymerization mode may be solutionpolymerization or slurry polymerization. Further, as the case requires,a known method such as batch polymerization, continuous polymerization,preliminary polymerization or multi step polymerization, may beemployed.

[0126] Linear or loop, single or connected plural pipe polymerizers mayalso be employed. In such a case, the pipe polymerizers may have variousknown mixers such as dynamic or static mixers or static mixers equippedwith a cooling means, or various known coolers such as coolers equippedwith cooling slender pipes. Further, they may have a batch typepreliminary polymerizer. Further, a method such as gas phasepolymerization may be employed.

[0127] The temperature for polymerization is suitably from −78° C. to200° C. A polymerization temperature lower than −78° C., is industriallydisadvantageous, and if it exceeds 200° C., decomposition of thetransition metal compound tends to take place, such being undesirable.

[0128] Industrially more preferably, it is from 0° C. to 160° C.,particularly preferably from 30° C. to 160° C.

[0129] The pressure during the polymerization is usually from 0.1 atm to1000 atm, preferably from 1 to 100 atm, particularly industriallypreferably from 1 to 30 atm.

[0130] When alumoxane (or aluminoxane) is used as a cocatalyst, it isused in a ratio to the metal of the transition metal compound of from0.1 to 100,000, preferably from 10 to 10,000, by a ratio of aluminumatom/metal atom of the transition metal compound. If the ratio issmaller than 0.1, the transition metal compound cannot effectively beactivated, and if it exceeds 100,000, such being economicallydisadvantageous.

[0131] When a boron compound is used as a cocatalyst, it is used in aratio of from 0.01 to 100, preferably from 0.1 to 10, particularlypreferably 1, by a ratio of boron atom/metal atom of the transitionmetal compound.

[0132] If the ratio is smaller than 0.01, the transition metal compoundcannot effectively be activated, and if it exceeds 100, such beingeconomically disadvantageous.

[0133] The transition metal compound and the cocatalyst may be mixed andprepared outside the polymerization tank, or may be mixed in the tank atthe time of polymerization.

[0134] In the first polymerization step of the present invention, theolefin partial pressure may be continuously or stepwisely changed withina range of more than 50% and less than 150%, relative to the olefinpartial pressure at the initiation of the polymerization. The olefinpartial pressure in the first polymerization step is preferablymaintained to be constant during the polymerization.

[0135] Further, in the first polymerization step of the presentinvention, the concentration of the aromatic vinyl compound in thepolymerization solution can be continuously or stepwisely changed withina range of more than 30% and less than 200%, relative to theconcentration at the initiation of the polymerization. Further, it ispreferred to set the conversion of the aromatic vinyl compound monomerat a level of less than 70% (to set the aromatic vinyl compoundconcentration higher by more than 30% as compared with the initiation ofthe polymerization) without carrying out divided addition of thearomatic vinyl compound monomer.

[0136] Olefin/aromatic Vinyl Compound/diene Copolymer to be Used in thePresent Invention

[0137] The olefin/aromatic vinyl compound/diene copolymer to be used inthe present invention can be synthesized from the respective monomers ofan aromatic vinyl compound, an olefin and a diene by means of a singlesite coordination polymerization catalyst in the above-described firstpolymerization step.

[0138] As the olefin/aromatic vinyl compound/diene copolymer obtained inthe first polymerization step (the main chain polymerization step) ofthe present invention, preferred is an ethylene/styrene/diene copolymer,an ethylene,/styrene/α-olefin/diene copolymer or anethylene/styrene/cyclic olefin/diene copolymer, and particularlypreferably, an ethylene/styrene/diene copolymer, may be employed.

[0139] Further, the olefin/aromatic vinyl compound/diene copolymerobtained in the first polymerization step (the main chain polymerizationstep) of the present invention may have a cross structure or acrosslinked structure with the contained diene monomer units, but it isnecessary that the gel content is less than 10 weight %, preferably lessthan 0.1 weight %, of the entirety.

[0140] Now, a typical suitable ethylene/styrene/diene copolymer to beused in the present invention, will be described.

[0141] The ethylene/styrene/diene copolymer obtained by the firstpolymerization step (the main chain polymerization step) preferably hasa chain structure of head-to-tail styrene units attributable to peaksobserved at from 40 to 45 ppm by the 13C-NMR measurement based on TMS.Further, it is preferred to have a chain structure of styrene unitsattributable to peaks observed at 42.3 to 43.1 ppm, 43.7 to 44.5 ppm,40.4 to 41.0 ppm and 43.0 to 43.6 ppm.

[0142] Further, the copolymer to be suitably used in the presentinvention, is an ethylene/styrene/diene copolymer obtainable by means ofa metallocene catalyst capable of producing an isotactic polystyrene byhomopolymerization of styrene, and an ethylene/styrene/diene copolymerobtainable by means of a metallocene catalyst capable of producingpolyethylene by homopolymerization of ethylene.

[0143] Therefore, the obtained ethylene/styrene/diene copolymer may haveethylene chain structures, head-to-tail styrene chain structures andstructures having ethylene units and styrene units bonded, in its mainchain.

[0144] On the other hand, with conventional so-called pseudo-randomcopolymers, no styrene head-to-tail chain structure is observed evenwhen the styrene content is in the vicinity of the maximum of 50 mol %.Further, even if homopolymerization of styrene is attempted by means ofa catalyst for the preparation of a pseudo-random copolymer, no polymercan be obtained. Depending upon the polymerization conditions, etc., avery small amount of atactic styrene homopolymer may sometimes beobtainable, but this should be understood to have been formed by cationpolymerization or radical polymerization due to methylalumoxane which iscoexists or due to an alkylaluminum included therein.

[0145] The ethylene/styrene/diene copolymer obtainable in the firstpolymerization step (the main chain polymerization step) to bepreferably employed in the present invention, is a copolymer wherein thestereoregularity of phenyl groups in the alternating structure ofstyrene and ethylene represented by the following general formula (4)contained in its structure, is such that the isotactic diad index (orthe meso diad index) m is larger than 0.5, preferably larger than 0.75,particularly preferably larger than 0.95.

[0146] The isotactic diad index m of the alternating copolymer structureof ethylene and styrene, can be obtained by the following formula (ii)from an area Ar of the peak attributable to the r structure of themethylene carbon peak and an area Am of the peak attributable to the mstructure appearing in the vicinity of 25 ppm:

m=Am/(Ar+Am)  Formula (ii)

[0147] The positions of the peaks may sometimes shift more or lessdepending upon the measuring conditions or the solvent. For example,when chloroform-d is used as a solvent, and TMS is used as standard, thepeak attributable to the r structure appears in the vicinity of from25.4 to 25.5 ppm, and the peak attributable to the m structure appearsin the vicinity of from 25.2 to 25.3 ppm.

[0148] Further, when tetrachloroethane-d2 is used as a solvent, and thecenter peak at 73.89 ppm of the triplet of tetrachloroethane-d2 is usedas standard, the peak attributable to the r structure appears in thevicinity of from 25.3 to 25.4 ppm, and the peak attributable to the mstructure appears in the vicinity of from 25.1 to 25.2 ppm.

[0149] Here, the m structure represents a meso diad structure, and the rstructure represents a racemic diad structure.

[0150] The ethylene/styrene/diene copolymer to be obtained in the firstpolymerization step (the main chain polymerization step) is preferably acopolymer wherein the alternating structure index λ (represented by thefollowing formula (i)) indicating the proportion of the alternatingstructure of styrene and ethylene represented by the general formula (4)contained in the copolymer structure, is smaller than 70 and larger than0.01, preferably smaller than 30 and larger than 0.1.

λ=A3/A2×100  Formula (i)

[0151] wherein A3 is the sum of areas of three peaks a, b and cattributable to an ethylene/styrene alternating structure represented bythe following general formula (4′), obtained by the 13C-NMR measurement,and A2 is the sum of areas of peaks attributable to the main chainmethylene and methane carbon, as observed within a range of from 0 to 50ppm by 13C-NMR using TMS as standard.

[0152] (wherein Ph represents a phenyl group and x represents the numberof repeating units and is an integer of at least 2.)

[0153] For at ethylene/styrene/diene copolymer having a diene content ofat most 3 mol %, preferably less than 1 mol %, it is effective to havehead-to-tail styrene chains and/or to have isotactic stereoregularity inthe ethylene/styrene alternating structure, and/or to have analternating structure index λ of smaller than 70, so that it will be anelastomer copolymer having a high transparency and high mechanicalstrength such as breaking strength. A copolymer having suchcharacteristics can be suitably employed in the present invention.

[0154] Especially, a copolymer having a high level of isotacticstereoregularity in the ethylene/styrene alternating structure and analternating structure index λ of smaller than 70, is preferred as thecopolymer of the present invention. Further, a copolymer having ahead-to-tail styrene chain, an isotactic stereoregularity in theethylene/styrene alternating structure, and an alternating structureindex λ of smaller than 70, is particularly preferred as the copolymerof the present invention.

[0155] Namely, a preferred ethylene/styrene/diene copolymer of thepresent invention has a characteristic such that it has an alternatingstructure of ethylene and styrene having high stereoregularity and atthe same time has various structures such as ethylene chains havingvarious lengths, inversion bonds of styrene and styrene chains havingvarious lengths simultaneously. Further, the ethylene/styrene/dienecopolymer of the present invention has a characteristic such that theproportion of the alternating structure can be variously changeable bythe content of styrene in the copolymer, the polymerization catalyst orthe polymerization conditions employed, within such a range that thevalue λ obtained by the above formula is more than 0.01 and less than70.

[0156] It is important that the alternating index λ is lower than 70 inorder to present significant mechanical strength, solvent resistance,toughness and transparency despite a crystallizable polymer, or in orderto be a partially crystallizable polymer, or in order to be anon-crystallizable polymer.

[0157] The above-described olefin/aromatic vinyl compound/dienecopolymer to be preferably employed in the present invention,particularly an ethylene/styrene/divinylbenzene copolymer, can beobtained by means of a polymerization catalyst comprising a transitionmetal compound represented by the above general formula (1) and acocatalyst.

[0158] In the foregoing, as a typical preferred example of theolefin/aromatic vinyl compound/diene copolymer to be used in the presentinvention, an ethylene/styrene/diene copolymer has been described, butthe olefin/aromatic vinyl compound/diene copolymer to be used in thepresent invention is not, of course, limited to this.

[0159] The weight average molecular weight of the olefin/aromatic vinylcompound/diene copolymer to be used in the present invention is at least10,000, preferably at least 30,000, particularly preferably at least60,000, and at moist 1,000,000 preferably at most 500,000. The molecularweight distribution (Mw/Mn) is not particularly limited, but is usuallyat most 6, preferably at most 4, most preferably at most 3.

[0160] Here, the weight average molecular weight is a molecular weightcalculated as polystyrene obtained by using standard polystyrene by GPC.The same will apply to the following description.

[0161] The weight average molecular weight of the olefin/aromatic vinylcompound/diene copolymer to be used in the present invention can beadjusted as the case requires, within the above range, by a known methodemploying a chain transfer agent such as hydrogen or by changing thepolymerization temperature.

[0162] The olefin/aromatic vinyl compound/diene copolymer obtainable inthe first polymerization step (the main chain polymerizations step) ofthe present invention may have a partially crossing structure orbranched structure via diene units contained.

[0163] Further, another embodiment of the present invention is anolefin/aromatic vinyl compound/divinylbenzene copolymer having anaromatic vinyl compound content of from 0 mol % to 96 mol %, preferablyfrom 0.03 mol % to 96 mol %, a diene content of from 0.0001 mol % to 3mol %, the rest being an olefin, obtained by copolymerizingm-divinylbenzene having an isomer purity of at least 80 weight %,preferably at least 90 weight %, an olefin and an aromatic vinylcompound. Such an olefin/aromatic vinyl compound/divinylbenzenecopolymer can be obtained by the process disclosed in the presentinvention, and it is useful preferably for the production of thecross-copolymerized olefin/aromatic vinyl compound/diene copolymer ofthe present invention. Further, it may be used for other applications,such as for the production of a cross-linked polymer, by e.g. a radicalmethod or electron ray cross linking, or as a resin additive or amodifying material.

[0164] B) Second Polymerization Step (Crossing Step)

[0165] As the second polymerization step of the present invention,coordination polymerization employing the above-mentioned single sitecoordination polymerization catalyst, is employed. Preferably, a singlesite coordination polymerization catalyst comprising a transition metalcompound represented by the same general formula (1) as in the firstpolymerization step and a cocatalyst, is employed. This single sitecoordination polymerization catalyst comprising a transition metalcompound represented by the general formula (1) and a cocatalyst, iscapable of copolymerizing residual coordination polymerizable doublebonds of diene units, particularly divinylbenzene, copolymerized to thepolymer main chain, at high efficiency, and it is preferred in thepresent invention. In the second polymerization step of the presentinvention, it is most preferred, to employ the same single sitecoordination polymerization catalyst as used in the first polymerizationstep, (the same transition metal compound, and the same cocatalyst). Thecopolymer obtainable in the second polymerization step of the presentinvention preferably has the same structure as the copolymer in theabove-mentioned first polymerization step.

[0166] In the second polymerization step of the present invention, thesame method as the polymerization method employed, in theabove-mentioned first polymerization step, is employed. In this case,the respective monomers employed in the above-mentioned firstpolymerization step, the olefin, the aromatic vinyl compound, and, ifnecessary, the diene remaining in the polymerization solution, may beemployed.

[0167] The second polymerization of the present invention is preferablycarried out following the first polymerization step by using thepolymerization solution obtained in the above first polymerization step.However, the second polymerization step may be carried out in thepresence of a single site coordination polymerization catalyst byrecovering the copolymer obtained in the above first polymerization stepfrom the polymerization solution, dissolving it in a new solvent andadding monomers to be employed.

[0168] The aromatic vinyl compound content is required to be differentby at least 5 mol %, preferably 10 mol %, most preferably at least 15mol %, as between the olefin/aromatic vinyl compound/diene copolymer tobe polymerized in the first polymerization step (the main chainpolymerization step), of the present invention and the olefin/aromaticvinyl compound copolymer or the olefin/aromatic vinyl compound/dienecopolymer to be polymerized in the second or subsequent polymerizationstep (the crossing step) (when the polymerization solution obtained inthe first polymerization step is used as it is, in the second orsubsequent polymerization step, the resulting polymer will have a smallamount of a residual diene copolymerized). In an extreme case, thearomatic vinyl compound content in the olefin/aromatic vinyl compoundcopolymer to be polymerized in the second or subsequent polymerizationstep (the crossing step) may be 0 mol %. In this case, it is preferredto carry out the second polymerization step by recovering the copolymerfrom the polymerization solution obtained in the first polymerizationstep and dissolving it in a new solvent, and adding a catalyst, acocatalyst and an olefin.

[0169] Further, the aromatic vinyl compound content in theolefin/aromatic vinyl compound/(diene copolymer obtainable in the firstpolymerization step and the aromatic vinyl compound content in thefinally obtainable cross-copolymerized olefin/aromatic vinylcompound/diene copolymer, are required to be different by at least 2 mol%, preferably at least 5 mol %, more preferably at least 10 mol %.

[0170] The polymer obtainable in the second polymerization step (thecross chain polymerization step) of the present invention may have apartially crossing structure or a branched structure via diene unitscontained.

[0171] In a case where the polymerization solution obtained in the firstpolymerization step is employed in the second polymerization step, anunreacted diene remaining in the polymerization solution will becopolymerized in the second polymerization step, and the diene contentis usually within a range of from 0.0001 mol % to 3 mol %, preferablyfrom 0.001 mol % to less than 0.5 mol %, in the olefin/aromatic vinylcompound copolymer (inclusive of cross chains) to be obtained in thesecond polymerization step. If the diene content is higher than thisrange, the finally obtainable cross copolymer tends to be insolubilizedor gelled to deteriorate the processability, such being undesirable.

[0172] A specific process for producing the cross-copolymer of thepresent invention, which satisfies the foregoing, will be describedbelow.

[0173] Namely, it is a process for producing a cross-copolymerizedolefin/aromatic vinyl compound/diene copolymer, employing apolymerization method of at least two steps comprising as the firstpolymerization step (the main chain polymerization step) carrying outcopolymerization of an aromatic vinyl compound monomer, an olefinmonomer and a diene monomer by means of a coordination polymerizationcatalysts to synthesize an olefin/aromatic vinyl compound/dienecopolymer, and then as the second polymerization step (the crossingstep) under polymerization conditions different therefrom, carrying outpolymerization by means of a coordination polymerization catalyst in theco-existence of this olefin/aromatic vinyl compound/diene copolymer andat least an olefin and an aromatic vinyl compound monomer. Further,preferred is a process satisfying at least one of the followingconditions.

[0174] 1) The olefin partial pressure of the polymerization system inthe second or subsequent polymerization step is at least 150% or at most50%, relative to the olefin partial pressure at the initiation of thefirst polymerization step. However, industrially, the olefin partialpressure in the second or subsequent polymerization step is at most 1000atm, preferably at most 100 atm.

[0175] On the other hand, in the present invention, the olefin partialpressure in the first, polymerization step is adjusted within a range ofhigher than 50% and lower than 150% of the olefin pressure at theinitiation of the polymerization, but the olefin partial pressure ismore preferably constant.

[0176] 2) The concentration of the aromatic vinyl compound in thepolymerization solution at the initiation of the second or subsequentpolymerization step is at most 30% or at least 200%, relative to theconcentration of the aromatic vinyl compound at the initiation of thefirst polymerization step.

[0177] However, the concentration of the aromatic vinyl compound in thefirst step in the present invention, is maintained within a range higherthan 30% of the concentration at, the initiation of the polymerization.

[0178] 3) In the first polymerization step and the second or subsequentpolymerization step, different single site coordination polymerizationcatalysts are employed.

[0179] 4) In the first polymerization step and the second or subsequentpolymerization step, the type of the olefin to be used forpolymerization is different.

[0180] The first polymerization step and the second polymerization stepare distinguished at such a time point that an operation for such changeof conditions has been initiated, or at such a time point that suchchange of conditions has been satisfied.

[0181] The change to satisfy the above conditions is preferably carriedout and completed as quickly as possible, preferably within 50%, morepreferably within 30%, most preferably within 10% of the polymerizationtime in the second polymerization step.

[0182] The polymerization temperatures in the first polymerization stepand the second polymerization step are preferably the same. If they aredifferent, the temperature difference is suitably within about 100° C.

[0183] As a method for changing the compositional ratio of monomers inthe polymerization solution, a method is available wherein the olefinpartial pressure of the polymerization system in the second orsubsequent polymerization step is changed at least 150%, preferably200%, most preferably at least 300%, relative to the firstpolymerization step. For example, in a case where ethylene is employedas the olefin, when the first polymerization step is carried out underan ethylene pressure of 0.2 MPa, the second polymerization step iscarried out under a pressure of at least 0.3 MPa, preferably at least0.4 MPa, most preferably at least 0.6 MPa.

[0184] Further, the olefin partial pressure of the polymerization systemin the second or subsequent polymerization step may be changed to atmost 50%, preferably at most 20%, relative to the first polymerizationstep. For example, when the first polymerization step is carried outunder an ethylene pressure of 1.0 MPa, the second polymerization step iscarried out under a pressure of almost 0.5 MPa, preferably at most 0.2MPa.

[0185] The olefin pressure in the second polymerization step may beconstant or changed stepwisely or continuously during the polymerizationso long as it satisfies the above conditions.

[0186] Further, as a method for changing the compositional ratio ofmonomers in the polymerization solution, a method may be employedwherein the concentration of the aromatic vinyl compound in thepolymerization solution at the initiation of the polymerization in thesecond or subsequent polymerization step, is changed to at most 30%,preferably at most 20%, or at least 200%, preferably at least 500%,relative to the first polymerization step. For example, in a case wherestyrene is employed as the aromatic vinyl compound, when the firstpolymerization step is initiated at a styrene concentration in thepolymerization solution of 1 mol %/l, the second polymerization step iscarried out at a concentration of at most 0.5 mol/l, preferably at most0.2 mol/l, or at least 2 mol/l, preferably at least 5 mol/l. Further,changes of the above olefin partial pressure and the concentration ofthe aromatic vinyl compound may be applied in combination.

[0187] When the second polymerization step is carried out in thepresence of a single site coordination polymerization catalyst byrecovering the copolymer obtained in the first polymerization step fromthe polymerization solution and dissolving it in a new solvent, andadding an olefin and an aromatic vinyl compound monomer, it is possibleto employ a single site polymerization catalyst which is different fromthe first polymerization step.

[0188] By changing the type of the olefin to be used for thepolymerization in the first polymerization step and the second orsubsequent polymerization step, the content of the aromatic vinylcompound in the copolymer polymerized in the first polymerization step,and the second polymerization step or the content of the aromatic vinylcompound in the cross-copolymer finally obtainable, can be changed asdescribed above.

[0189] In a case where the second polymerization step is carried outcontinuously after the first polymerization step employing thepolymerization solution obtained in the above first polymerization step,and the monomers remaining in the polymerization solution of the firstpolymerization step are used for the second polymerization step withoutaddition of a new aromatic vinyl compound monomer, the conversion of thearomatic vinyl compound monomer species throughout the entirepolymerization steps is preferably at least 50 weight %, particularlypreferably at least 60 weight %. As the conversion of the aromatic vinylcompound monomer becomes higher, the probability that the polymerizabledouble bonds of diene units in the main chain of the copolymer arecross-copolymerized, will increase.

[0190] For the production of the cross-copolymer of the presentinvention, it is preferred to employ a process which satisfies 1) and 2)among the above conditions.

[0191] Namely, in the second polymerization step, it is preferred toemploy the same, single site coordination polymerization catalyst (thesame transition metal compound and the same cocatalyst) as in the firstpolymerization step.

[0192] Further, it is preferred that in the first polymerization stepand the second or subsequent polymerization step, the type of the olefinto be used for polymerization is the same.

[0193] Further, for the production of the cross-copolymer of the presentinvention, it is most preferred to employ a process which satisfies 1)among the above conditions.

[0194] For the production of the cross-copolymer of the presentinvention, most preferably, a method is employed wherein the olefinpartial pressure of the polymerization system in the second orsubsequent polymerization step is changed at least 300%, relative to thefirst polymerization step.

[0195] Further, in a case where the olefin partial pressure in thesecond polymerization step is not constant, i.e. in a case where itvaries within the above range, most preferably, a method is employedwherein the olefin partial pressure in the second or subsequentpolymerization step is changed at least 300%, relative to the olefinpartial pressure at the initiation of the first polymerization step.

[0196] The proportion of the copolymer obtained in the firstpolymerization step is required to be at least 10 weight %, preferablyat least 30 weight % of the cross-copolymer finally obtainable. Further,the amount of the polymer (inclusive of the weight of cross chains)obtainable in the second polymerization step is required to be at least10 weight %, preferably at least 30 weight % of the cross-copolymerfinally obtainable. If the proportion of the copolymer obtained in thefirst polymerization step or in the second polymerization step is lessthan 10 weight % of the finally obtainable cross-copolymer, thecharacteristics of the copolymer of the small amount component can notadequately be obtained.

[0197] The first polymerization step and the second polymerization stepmay be carried out in separate reactors. These steps may be carried outby means of a single reactor. In such a case, these steps aredistinguished at such a time point that the operation for the change ofthe conditions as described in the above 1) to 4) has been initiated, orat such a time point that the change of such conditions has beensatisfied.

[0198] The cross-copolymer of the present invention may be produced in asingle reactor by carrying out copolymerization of an olefin, anaromatic vinyl compound and a diene by means of a coordinationpolymerization catalyst while changing the olefin or aromatic vinylcompound, concentration continuously. It will suffice that at least theof the condition changes of the above 1) to 4) is satisfiedsubstantially at the initiation and completion of the polymerization.

[0199] Further, the cross-copolymer of the present invention is across-copolymer excellent in the mold processability, characterized inthat MFR (melt flow rate) as measured under a load of 5 kg at 230° C. isat least 1.0 g/10 min and at most 50 g/10 min. A process for producingsuch a cross-copolymer of the present invention is not particularlylimited, but a process which satisfies at least one of the followingproduction conditions, is preferred.

[0200] a) In the first and/or second polymerization step, thepolymerization temperature is substantially always at least 80° C.,preferably at least 85° C. and at most 160° C.

[0201] b) The aromatic vinyl compound content of the polymer obtained inthe first polymerization step, is at least 30 mol %, and its weightaverage molecular weight is at most 250,000.

[0202] c) The diene to be employed, is m-divinylbenzene having an isomerpurity of at least 80 weight %, preferably at least 90 weight %.

[0203] The cross-copolymer of the present invention can be produced by aprocess comprising the above-mentioned first polymerization step (themain chain polymerization step) and the second polymerization step (thecrossing step). For this process, a conventional optional method may beemployed. For example, a method may be employed wherein the firstpolymerization step is carried out by completely mixed type batchpolymerization or continuous polymerization, and the secondpolymerization step is carried out also by similar batch polymerizationor continuous polymerization, or a method may be employed wherein thefirst polymerization step is carried out by completely mixed type batchpolymerization or continuous polymerization, and the secondpolymerization step is carried out by plug flow polymerization. Here,completely mixed type polymerization is a conventional method wherein,for example, a tank-form, a tower form or loop-form reactor is employed,and it is a polymerization method wherein in the reactor, thepolymerization solution is stirred and mixed relatively well to have asubstantially uniform composition. Further, plug flow polymerization isa polymerization method wherein in the reactor, mass transfer isrestricted, and the polymerization solution has a continuous ornon-continuous compositional distribution from the inlet towards theoutlet of the reactor. In the second polymerization step of the presentinvention, a polymerization means of a loop type or a plug flow typehaving a pipe-form equipped with various cooling and mixing means ispreferred with a view to carrying out heat removal efficiently, sincethe viscosity of the polymerization solution increases.

[0204] Now, the physical properties of a cross-polymerizedethylene/styrene/divinylbenzene copolymer as a typical example of thecross-copolymerized olefin/aromatic vinyl compound/diene copolymer ofthe present invention, and the applications thereof will be described.

[0205] The cross-copolymer of the present invention is characterized inthat the compositions (the styrene contents) of the main chain and thecross chain are substantially different. Either the main chain or thecross chain may have a composition having a low styrene content (i.e. acrystal structure derived from ethylene chains). Further, thecross-copolymer of the present invention may contain ethylene/styrenecopolymers (which may contain a small amount of divinylbenzene) havingdifferent styrene contents corresponding respectively to the styrenecontents of the main chain and the cross chain in an optional ratio.However, since the cross-copolymer functions as a compatibilizing agentfor them, it can have various characteristics and high transparency atthe same time.

[0206] The cross-copolymer of the present invention has good heatresistance, since it has a crystal structure derived from ethylenechains. Further, it can also have characteristics such as highmechanical properties (breaking strength, tensile modulus) and a lowglass transition temperature or a low brittle temperature (at most −50°C.) which an ethylene/styrene copolymer having a low styrene contenthas. Further, either the main chain or the cross chain can have acomposition having a relatively high styrene content, whereby theproduct can have the characteristics of an ethylene/styrene copolymerhaving a relatively high styrene content, as described below. Namely, itcan have a relatively low tensile modulus, surface hardness,flexibility, a tan δ component in the vicinity of room temperature inthe is viscoelasticity spectrum (0.05 to 0.80 at 0° C. or 25° C.), anantiscratching property, a feeling like polyvinyl chloride, a paintingproperty and printability.

[0207] Further, with the cross-copolymer of the present invention, thehardness can optionally be changed within the scope of a soft resin froma relatively hard resin (a shore A hardness of at least 88) to a softresin (a shore A hardness of at most 87 and at least about 60) bychanging the weight ratio of the main chain copolymer (the copolymercomponent obtained in the first polymerization step) and the cross chaincopolymer (the copolymer component obtained in the second polymerizationstep). Particularly, in order to make the shore A hardness of thecross-copolymer of the present invention to be at most 87, it ispreferred that either copolymer obtained in the first polymerizationstep or the second polymerization step is substantially non-crystalline,and this substantially non-crystalline copolymer occupies at least 60weight % in the finally obtainable cross-copolymer. Further, it isparticularly preferred that the copolymer obtained in the firstpolymerization step is substantially non-crystalline, and thissubstantially non-crystalline copolymer occupies at least 60 weight % ofthe finally obtainable cross copolymer. Here, substantiallynon-crystalline means that the melting point of the crystal peakobserved by DSC is at most 70° C., more preferably, its heat of fusionis at most 15 J/g, or the crystallinity (crystallization ratio)calculated by an X-ray diffraction method is at most 10%. Further, forthe shore A hardness of the cross-copolymer of the present invention tobe at most 87 at room temperature, it is important that the glasstransition point of the copolymer obtained in the first polymerizationstep is at most 5° C., preferably at most 0° C.

[0208] The cross-copolymerized ethylene/styrene/diene copolymer of thepresent invention may be used alone and can suitably be employed as asubstitute for a known transparent soft resin such as soft polyvinylchloride.

[0209] To the cross-copolymer of the present invention, a stabilizer, anaging-preventing agent, a light resistance-improving agent, anultraviolet absorber, a plasticizer, a softening agent, a lubricant, aprocessing adjuvant, a colorant, an antistatic agent, an anti-foggingagent, a blocking-preventing agent, a crystal nucleating agent, etc.which are commonly used for resins, may be incorporated. These additivesmay be used alone or in combination of a plurality of them.

[0210] By virtue of the excellent characteristics, the cross-copolymerof the present invention is used alone or as a composition containing itas the main component and can be suitably used for a stretch film, ashrink film, a packaging material, a sheet, a tube or a hose as asubstitute for a known transparent soft resin such as soft polyvinylchloride.

[0211] Application to Films

[0212] In a case where the cross-copolymer of the present invention isused as a film or a stretch packaging film, the thickness is notparticularly limited, but it is usually from 3 μm to 1 mm, preferablyfrom 10 μm to 0.5 mm. To use it as a stretch packaging film for foods,the thickness is preferably from 5 to 100 μm, more preferably from 10 to50 μm.

[0213] For the production of a transparent film or a stretch packagingfilm made of the cross-copolymer of the present invention, a commonextrusion film-forming method such as an inflation system or a T-diesystem, may be employed. For the purpose of improving the physicalproperties, the film or the stretch packaging film of the presentinvention may be laminated with other suitable film, for example, a filmof e.g. isotactic or syndiotactic polypropylene, high densitypolyethylene, low density polyethylene (LDPE or LLDPE), polystyrene,polyethylene terephthalate or an ethylene/vinyl acetate copolymer (EVA).

[0214] Further, the film or the stretch packaging film of the presentinvention may have self-tackiness or an adhesive property by suitablyselecting the composition of the main chain or the cross chain. However,if a stronger self-tackiness is required, it may be laminated with otherfilm having self-tackiness to obtain a multi-layered film.

[0215] Further, when a stretch packaging film having a non-tacky surfaceand a tacky surface on the front and rear sides, is desired, thenon-tacky surface may be made of an ethylene/styrene copolymer having ahigher ethylene content or a linear low density polyethylene having adensity of at least 0.916 g/cm³ in a thickness of from 5 to 30% of thetotal thickness, the interlayer may be made of the ethylene/styrenecopolymer to be used in the present invention, and the tacky layer maybe made of one having from 2 to 10 weight % of liquid polyisobutylene,liquid polybutadiene or the like incorporated to the ethylene/styrenecopolymer to be used in the present invention, one having from 2 to 10weight % of liquid polyisobutylene, liquid polybutadiene or the likeincorporated to a linear low density polyethylene having a density of atleast 0.916 g/cm³, or an ethylene/vinyl acetate copolymer, in athickness of from 5 to 30% of the total thickness, to obtain amultilayer film. Otherwise, it is also possible to incorporate asuitable tackifier in a suitable amount.

[0216] Specific applications of the film of the present invention arenot particularly limited, but it is useful as a general packagingmaterial or a container and can be used for e.g. a packaging film, a bagor a pouch. Especially, it can suitably be used as a stretch packagingfilm or a pallet stretching film for food packaging.

[0217] To the molded product, particularly the film or the stretchpackaging film, of the present invention, surface treatment with e.g.corona, ozone or plasma, coating with an anti-fogging agent, coatingwith a lubricant or printing, may be applied, as the case requires.

[0218] Among molded products of the present invention, the film or thestretch packaging film may be prepared as a monoaxially or biaxiallystretched film, as the case requires.

[0219] The film or the stretch packaging film of the present inventionmay be bonded to the film itself or to a material such as otherthermoplastic resin by fusion by means of e.g. heat, supersonic waves,microwave or by bonding by means of e.g. a solvent.

[0220] Further, when used as a stretch packaging film for foods, it canbe suitably packaged by an automatic packaging machine or a manualpackaging machine.

[0221] Further, when the film of the present invention has a thicknessof, for example, at least 100 μm, a packaging tray for foods, electricalproducts, etc., can be molded by a technique such has heat molding,vacuum molding, compression molding or air-pressure forming.

[0222] Further, the cross-copolymer of the present invention basicallydoes not contain an elutable plasticizer or halogen and thus has a basiccharacteristic that its environmental compatibility or safety is high.

[0223] The cross-copolymer of the present invention may be used as acomposition with other polymers.

[0224] Known polymers or additives for the conventional compositionswith an ethylene/styrene copolymer, can also be employed for acomposition with the cross-copolymer of the present invention. Thefollowing may be mentioned as such polymers and additives. The followingpolymers may be added within a range of from 1 to 99 parts by weight,preferably from 30 to 95 parts by weight, based on the compositionemploying the cross-copolymer of the present invention. Further, thecross-copolymer of the present invention can be used also as acompatibilizing agent for “an aromatic vinyl compound type polymer” and“an olefin type polymer”. With the cross-copolymer of the presentinvention, the olefin/aromatic vinyl compound content ratio in the mainchain and the cross chain can substantially be changed, whereby it ispossible to increase the compatibility with the respective polymers, andit is suitably employed as a compatibilizing agent for that purpose. Inthis case, the cross-copolymer of the present invention can be usedwithin a range of from 1 to 50 parts by weight, preferably from 1 to 20parts by weight, based on the composition. Further, in the case of “afiller” or “a plasticizer”, it can be used within a range of from 1 to80 parts by weight, preferably from 5 to 50 parts by weight, based onthe composition.

[0225] Aromatic Vinyl Compound Type Polymer

[0226] A homopolymer of an aromatic vinyl compound, and a copolymer ofan aromatic vinyl compound with at least one monomer componentcopolymerizable therewith, wherein the aromatic vinyl compound contentis at least 10 weight %, preferably at least 30 weight %. The aromaticvinyl compound monomer to be used for the aromatic vinyl compound typepolymer includes styrene and various substituted styrenes such asp-methylstyrene, m-methylstyrene, o-methylstyrene, o-t-butylstyrene,m-t-butylstyrene, p-t-butylstyrene and α-methylstyrene, and further, acompound having a plurality of vinyl groups in one molecule, such asdivinylbenzene, may also be mentioned. Further, a copolymer of aplurality of such aromatic vinyl compounds, may also be employed. Thestereoregularity among mutual aromatic groups of the aromatic vinylcompound may be atactic, isotactic or syndiotactic.

[0227] The monomer copolymerizable with the aromatic vinyl compoundincludes butadiene, isoprene, other conjugated dienes, acrylic acid,methacrylic acid and amide derivatives or ester derivatives, maleicanhydride and its derivatives. The copolymerization mode may be any oneof block copolymerization, tapered block copolymerization, randomcopolymerization and alternating copolymerization. Further, it may beone having the above aromatic vinyl compound graft-polymerized to apolymer made of the above-mentioned monomers, which contains at least 10weight %, preferably at least 30 weight %, of the aromatic vinylcompound.

[0228] The above aromatic vinyl compound type polymer is required tohave a weight average molecular weight of at least 30,000, preferably atleast 50,000, as calculated as styrene, in order to show the performanceas a practical resin.

[0229] The aromatic vinyl compound type resin to be used, may, forexample, be isotactic polystyrene (i-PS), syndiotactic polystyrene(s-PS), atactic polystyrene (a-PS), rubber-reinforced polystyrene(HIPS), an acrylonitrile/butadiene/styrene copolymer (ABS) resin, astyrene/acrylonitrile copolymer (AS resin), a styrene/methacrylatecopolymer such as a styrene/methyl methacrylate copolymer, astyrete/diene block/tapered copolymer (such as SBS, SIS), ahydrogeonated styrene/diene block/tapered copolymer (such as SEBS,SEPS), a styrene/diene copolymer (such as SBR), a hydrogenatedstyrene/diene copolymer (such as hydrogenated SBR), a styrene/maleicacid copolymer, or a styrene/imidated maleic acid copolymer. Further, itis a concept including a petroleum resin.

[0230] Olefin Type Polymer

[0231] For example, low density polyethylene (LDPE), high densitypolyethylene (HDPE), linear low density polyethylene (LLDPE), isotacticpolypropylene (i-PP), is syndiotactic polypropylene (s-PP), atacticpolypropylene (a-PP), a propylene/ethylene block copolymer, apropylene/ethylene random copolymer, an ethylene/propylene/dienecopolymer (EPDM), an ethylene/vinyl acetate copolymer, polyisobutene,polybutene, a cyclic olefin polymer such as polynorbornene and a cyclicolefin copolymer such as an ethylene/norbornene copolymer, may bementioned. It may be an olefin type resin co-polymerized with a dienesuch as butadiene or α-ω-diene, as the case requires.

[0232] The above olefin type polymer is required to have a weightaverage molecular weight of at least 10,000, preferably at least 30,000,as calculated as styrene, in order to show the performance as apractical resin.

[0233] Other Resins, Elastomers and Rubbers

[0234] For example, polyamide such as nylon, polyimide, polyester suchas polyethylene terephthalate, polyvinyl alcohol, and a styrene typeblock copolymer such as SBS (styrene/butadiene block copolymer), SEBS(hydrogenated styrene/butadiene block copolymer), SIS (styrene/isopreneblock copolymer), SEPS (hydrogenated styrene/isoprene block copolymer),SBR (styrene/butadiene block copolymer) or hydrogenated SBR, which isnot in the scope of the above aromatic vinyl compound type resin,natural rubber, a silicone resin, and silicone rubber, may be mentioned.

[0235] Fillers

[0236] Known fillers may be employed. As preferred examples, calciumcarbonate, talc, clay, calcium silicate, magnesium carbonate, magnesiumhydroxide, mica, barium sulfate, titanium oxide, aluminum hydroxide,silica, carbon black, wood powder and wood pulp may, for example, bementioned. Further, glass fibers, known graphites or conductive fillerssuch as carbon fibers, may also be employed.

[0237] Plasticizers

[0238] Known plasticizers, such as paraffin type, naphthene type oraroma type process oils, mineral oil type softening agents such asliquid paraffin, castor oil, linseed oil, olefin type wax, mineral typewax and various esters, may be used.

[0239] For the production of the polymer composition of the presentinvention, a suitable known blending method may be employed. Forexample, melt-mixing can be carried out by means of a single screw ortwin screw extruder, a Banbury mixer, a plasto mill, a co-kneader or aheated roll. Prior to the melt mixing, it is advisable to uniformly mixthe respective materials by means of e.g. a Henschel mixer, a ribbonblender, a super mixer or a tumbler. The melt mixing temperature is notparticularly limited, but it is usually from 100 to 300° C., preferablyfrom 150 to 250° C.

[0240] As molding methods for various compositions of the presentinvention, known molding methods such as vacuum molding injectionmolding, blow molding, extrusion molding or profile extrusion molding,may be employed.

[0241] The composition containing the cross-copolymer of the presentinvention can be preferably used as various film or packaging materials,sheets, tubes, hoses, gaskets, and further as building materials such asfloor materials or wall materials, or interior materials forautomobiles.

[0242] Now, the present invention will be described with reference toExamples, but the present invention is by no means restricted to thefollowing Examples.

[0243] The analyses of copolymers obtained in the respective Examplesand Comparative Examples were carried out by the following methods.

[0244] The 13C-NMR spectrum was measured by using TMS as standard, byusing a chloroform-d solvent or a 1,1,2,2-tetrachloroethane-d2 solvent,by means of α-500 manufactured by Nippon Denshi Kabushiki Kaisha. Here,the measurement using TMS as standard is the following measurement.Firstly, using TMS as standard, the shift value of the center peak oftriplet 13C-NMR peaks of 1,1,2,2-tetrachloroethane-d2 was determined.Then, the copolymer was dissolved in 1,1,2,2-tetrachloroethane-d2, andthe 13C-NMR was measured, whereby each peak shift value was calculated,based on the triplet center peak of 1,2,2,2-tetrachloroethane-d2. Theshift value of the triplet center peak of 1,1,2,2-tetrachloroethane-d2was 73.89 ppm. The measurement was carried out by dissolving the polymerin such solvent in an amount of 3 weight/volume %.

[0245] The 13C-NMR spectrum measurement for quantitive analysis of peakareas, was carried out by a proton gate decoupling method having NOEerased, by using pulses with a pulse width of 45° and a repeating timeof 5 seconds as standard.

[0246] When the measurement was carried out under the same conditionsexcept that the repeating time was changed to 1.5 seconds, the measuredvalues of peak areas of the copolymer agreed to the values obtained inthe case where the repeating time was 5 seconds, within measurementerror.

[0247] The styrene content in the copolymer was determined by 1H-NMR. Asthe apparatus, α-500 manufactured by Nippon Denshi Kabushiki Kaisha andAC-250 manufactured by BRUCKER COMPANY, were employed. The determinationwas carried out at a temperature of from 80 to 100° C. by dissolving asample in 1,1,2,2-tetrachloroethane-d2 and comparing the intensity ofthe proton peak attributable to a phenyl group (6.5 to 7.5 ppm) and theproton peak attributable to an alkyl group (0.8 to 3 ppm), measured byusing TMS as standard.

[0248] The diene (divinylbenzene) content was measured by 1H-NMR.

[0249] As the molecular weights in Examples, weight average molecularweights as calculated as standard polystyrene, were obtained by means ofGPC (Gel Permeation Chromatography).

[0250] A copolymer soluble in THF at room temperature, was measured bymeans of HLC-8020manufactured-by TOSOH CORPORATION using THF as thesolvent.

[0251] A copolymer insoluble in THF at room temperature, was measuredeither at 135° C. by means of 150CV apparatus manufactured by WatersCompany using 1,2,4-trichlorobenzene as the solvent or at 145° C. bymeans of HLC-8121 apparatus manufactured by TOSOH CORPORATION usingo-chlorobenzene as the solvent. As the detector, RI (differentialrefractive index meter) was used. With cross-copolymers in Examples, therefractive index to o-dichlorobenzene as the solvent is reversed betweenthe main chain component and the cross chain component. Accordingly, themolecular weight of a cross-copolymer obtained by the RI detector is notaccurate and is useful only as a reference value.

[0252] The DSC measurement was carried out by using DSC 200 manufacturedby Seiko Denshi K.K. in a nitrogen stream at a temperature raising rateof 10° C./min. Using 10 mg of a sample, it was heated to 240° C. at atemperature raising rate of 20° C./min and quenched to −100° C. or lowerby liquid nitrogen (pretreatment), and then the temperature was raisedfrom −100° C. at a rate of 10° C./min to carry out the DSC measurementup to 240° C., whereby the melting point, the heat of crystal fusion andthe glass transition point were obtained. The glass transition point wasobtained by a tangent method.

[0253] As a sample for evaluation of the physical properties, a sheethaving thickness of 1.0 mm formed by a heat-pressing method(temperature: 180° C., time: 3 minutes, pressure: 50 kg/cm²) was used.

[0254] Tensile Test

[0255] In accordance with JIS K-6251, the sheet was cut into a shape oftest piece No. 1, and measured at a tensile speed of 500 mm/min by meansof AGS-100D model tensile tester manufactured by Shimadzu Corporation.

[0256] Permanent Elongation

[0257] The strain recovery in a tensile test was measured by thefollowing method.

[0258] Using the JIS No. 2 small size (½) test piece, it was pulled by atensile tester to a strain of 100% and maintained for 10 minutes, whereupon the stress was quickly released (without repulsion) and the strainrecovery after 10 minutes was represented by %.

[0259] Vicat Softening Point

[0260] A sheet having a thickness of 4 mm was prepared by a heatpressing method, and a test specimen of 10 mm×10 mm was cut out. Inaccordance with JIS K-7206, it was measured under a load of 320 g at aninitial temperature of 40° C. under a temperature raising condition of50° C./hr using HDT & VSPT tester S3-FH, manufactured by Toyo Seiki.

[0261] Measurement of Dynamic Viscoelasticity

[0262] Using a dynamic viscoelasticity measuring apparatus (RSA-II,manufactured by Rheometrix Company), the loss tan δ was measured at afrequency of 1 Hz within a temperature range of from −120° C. to +150°C. (the measuring temperature range was slightly changed depending uponthe properties of the sample). From a sheet having a thickness of 0.1 mmprepared by heat pressing, a sample for measurement (3 mm×40 mm) wasobtained.

[0263] X-ray Diffraction

[0264] The X-ray diffraction was measured by MXP-18 model high powerX-ray diffraction apparatus, manufactured by Mac Science Companyemploying as the ray source a Cu sealed counter cathode (wavelength:1.5405 Å).

[0265] Hardness

[0266] With respect to the hardness, durometer hardness of types A and Dwas obtained in accordance with the test method for durometer hardnessof plastics as prescribed in JIS K-7215. This hardness is aninstantaneous value.

[0267] Total Light Transmittance, Haze

[0268] With respect to the transparency, the total light transmittanceand the haze were measured by means of turbidity meter NDH2000,manufactured by Nippon Denshoku Kogyo K.K. in accordance with the testmethod for optical characteristics of plastics as prescribed in JISK-7105 with respect to a sheet having a thickness of 1 mm molded by heatpressing (temperature: 200° C., time: 4 minutes, pressure: 50 kg/cm²G).

[0269] Divinylbenzene

[0270] The divinylbenzene (a mixed product of m-isomer and p-isomer)used in the following Examples 1 to 3 relating to the cross-copolymerwas manufactured by Aldrich Company (purity as divinylbenzene: 80%, amixture of m-isomer and p-isomer, weight ratio ofmeta-form:para-form=70:30, accordingly, the isomer purity ofm-divinylbenzene is 70 weight %). In the following polymerization, when1 ml (5.5 mmol as divinylbenzene) was used per 400 ml of styrene, theamount of divinylbenzene corresponds to 1/640 of the amount of styreneby molar ratio.

[0271] Catalyst (Transition Metal Compound)

[0272] In the following Examples, as a transition metal compound(catalyst), rac-dimethylmethylenebis (4,5-benzo-1-indenyl)zirconiumdichloride, (rac-isopropylidenebis(4,5-benzo-1-indenyl)zirconiumdichloride) was employed.

[0273] rac-dimethylmethylenebis(4,5-benzo-1-indenyl)zirconium dichloride

EXAMPLE 1 Preparation of a Cross-copolymerizedEthylene/styrene/divinylbenzene Copolymer

[0274] Using rac-dimethylmethylenebis(4,5-benzo-1-indenyl)zirconiumdichloride as a catalyst, the preparation was carried out as follows.

[0275] Polymerization was carried out by means of an autoclave having acapacity of 10 l and equipped with a stirrer and a jacket for heatingand cooling.

[0276] 4400 ml of toluene, 400 ml of styrene and 1.0 ml ofdivinylbenzene manufactured by Aldrich Company were charged and heatedand stirred at an internal temperature of 70° C. About 200 l of nitrogenwas bubbled to purge the interior of the system and the polymerizationsolution. 8.4 mmol of triisobutyl aluminum and 21 mmol, based on Al, ofmethyl alumoxane (PMAO-3A, manufactured by TOSOH AKZO K.K.) were added,and ethylene was immediately introduced. After the pressure wasstabilized at 0.25 MPa (1.5 kg/cm²G), from a catalyst tank installedabove the autoclave, about 50 ml of a toluene solution having 8.4 μmolof rac-dimethylmethylenebis(4,5-benzo-1-indenyl)zirconium dichloride and0.84 mmol of triisobutyl aluminum dissolved therein, was added to theautoclave. Polymerization (the first polymerization step) was carriedout for 45 minutes while maintaining the internal temperature at 70° C.and the pressure at 0.25 MPa. At this stage, the amount of ethyleneconsumed was about 100 l in a standard state. A part of thepolymerization solution was sampled, and a polymer sample (polymer 1-A)of the first polymerization step was obtained by precipitation frommethanol. Ethylene was introduced rapidly, and the internal pressure wasbrought to 1.1 MPa in 25 minutes. By the increase of the ethylenepressure, polymerization was accelerated, whereby the internaltemperature rose from 70° C. up to 80° C. While maintaining the pressureat 1.1 MPa, polymerization was carried out for 70 minutes (the secondpolymerization step).

[0277] After completion of the polymerization, the obtained polymersolution was introduced in small portions into a large amount of amethanol solution which was vigorously stirred, to recover the polymer.This polymer was dried in air at room temperature for one day, and then,dried under vacuum at 80° C. until change in weight was no longer,observed. 805 g of the polymer (polymer 1-C) was obtained.

[0278] The polymerization conditions in the respective examples weresummarized in Table 1.

[0279] The analytical results of the polymers obtained in the respectiveExamples and Comparative Examples are shown in Table 2. TABLE 1Polymerization Conditions First polymerization step (main chainpolymerization step) Et Polymerization Et Polymerization Conversion (%)in Catalyst MAO St DVB Toluene pressure temperature consumption timefirst polymerization Ex. μmol mmol ml ml ml MPa ° C. amount l (min.)step % Ex. 1 8.4 P; 21 400 1.0 4400 0.25 70 About 100  64 38 Ex. 2 8.4P; 21 400 1.0 4400 0.25 70 About 150  96 45 Ex. 3 8.4 P; 21 400 1.0 44000.25 70 About 200 150 60 Second polymerization step (cross chainpolymerization step) Et St conversion pres- Et (%) in second Final Stsure Polymerization consumption Polymerization polymerization conversionEx. MPa temperture ° C. amount l time (min.) step Note 1 (%) Ex. 1 1.170-80 About 300 77 56 73 Ex. 2 1.1 70-80 About 370 81 56 75 Ex. 3 1.170-90 About 260 65 22 68 # polymerization step and measuring weightbalance from its polymer concentration and composition.)

[0280] TABLE 2 Polymerization Results Glass Heat of Styrene transitioncrystal Yield content temperature Melting fusion Ex. Polymers 1) g mol %Mw/10⁴ Mw/Mn ° C. point ° C. J/g Ex. 1 1-A 260 23.0 16.0 2.4 −18 None —1-B 545 7.6 — — — — — 1-C 805 11.6 (15.7) (4.7) −20 103 35 Ex. 2 2-A 35219.1 19.9 2.8 −18  48 17 2-B 543 6.5 — — — — — 2-C 895 10.7 (17.9) (4.8)−20 106 34 Ex. 3 3-A 470 18.9 19.4 2.9 −20  53 23 3-B 393 2.3 — — — — —3-C 863 9.8 (21.7) (4.1) −21 109 83

[0281] In Table 2, in addition to the polymer (1-A) obtained in thefirst polymerization step and the cross-copolymer i.e. the polymer (1-C)finally obtained through the second polymerization step, the weight andthe composition of the polymer (1-B) polymerized in the secondpolymerization step are also shown as determined from weight balance.

EXAMPLES 2 AND 3

[0282] Under the conditions shown in Table 1, polymerization and posttreatment were carried out in the same manner as in Example 1. By thegas chromatography analysis of the polymerization solution withdrawnupon completion of the first polymerization step, the amount ofdivinylbenzene remaining in the polymerization solution was obtained,and the amount of divinylbenzene consumed in the first polymerizationstep was obtained. From the value, the divinylbenzene content in thecopolymer obtained in each first polymerization step was obtained,whereby it was about 0.04 mol % with polymer 1-A, about 0.04 mol % withpolymer 2-A and about 0.07 mol % with polymer 3-A.

[0283] The structural index λ of the cross-copolymer obtained in eachExample and the isotactic diad index m of the styrene unit/ethylene unitalternating structure, were obtained in accordance with the aboveformulae (i) and (ii), respectively. λ values and m values obtained inExamples are shown in Table 3, and other results of measurements areshown in Tables 4 and 5. TABLE 3 St content Examples mol % λ value mvalue Example 1 1-A 23.0 16 >0.95 Example 1 1-C 11.6 10 >0.95 Example 22-A 19.1 14 >0.95 Example 2 2-C 10.7 8 >0.95 Example 3 3-A 19.1 15 >0.95Example 3 3-C 9.8 8 >0.95

[0284] TABLE 4 Example 1 Example 2 Example 3 Kind of polymer 1-C 2-C 3-CBreaking 517 500 500 elongation (%) Yield Yield point Yield point Yieldpoint strength was not was not was not (MPa) observed observed observedBreaking 34.9 35.8 31.2 strength (MPa) Elastic 29.5 29.2 38 modulus intension (MPa) 100% modulus 6.0 5.3 6.7 (MPa) 300% modulus 10.0 9.7 9.8(MPa) Hardness 88 88 90 (Shore A) Hardness 39 36 39 (Shore D) Totallight 80 83 81 transmittance (%) Haze (%) 15 13 17 Vicat 96 95 95softening point (° C.) MFR (g/10 min.) 0.13 0.06 Unmeasured 200° C.

[0285] TABLE 5 Gel content of polymer Example 1 (1-A) 0% Example 1 (1-C)0% Example 2 (2-A) 0% Example 2 (2-C) 0% Example 3 (3-A) 0% Example 3(3-C) 0%

[0286] In the Table, “0%” means “less than 0.1%”.

COMPARATIVE EXAMPLES 1 TO 6

[0287] Ethylene/styrene copolymers having various styrene contentsobtained by polymerization carried out in the method disclosed inEP-0872492A2 and JP-A-11-130808 usingrac-dimethylmethylenebis(4,5-benzo-1-indenyl)zirconium dichloride as acatalyst and methyl alumoxane (MAO) as a cocatalyst, are shown in Table6 TABLE 6 Glass St Melting transition content Mw/ Mw/ point point mol %10⁴ Mn ° C. ° C. Comparative R-1 5 18.5 2.1 103 −25 Example 1Comparative R-2 7 18.0 2.0 93 −28 Example 2 Comparative R-3 11 16.0 1.979 −22 Example 3 Comparative R-4 13 22.7 2.0 68 −23 Example 4Comparative R-5 17 17.5 2.0 63 −22 Example 5 Comparative R-6 21 18.5 2.0Unmeasured Unmeasured Example 6

COMPARATIVE EXAMPLE 7

[0288] Using a Brabender Plasti-Corder (PLE331 Model, manufactured byBrabender Company), 25 g of each of copolymers R-2 and R-6 was meltedand then kneading (external temperature: 180° C., rotational speed: 60RPM, time: 10 minutes) was carried out to obtain a composition. Theobtained ethylene/styrene copolymer composition was molded by theabove-mentioned press molding to obtain a sheet of 1 mm in thickness,and evaluation of various physical properties was carried out. In Tables7 and 8, the test results of the physical properties of the polymers ofComparative Examples and various polymers obtained, are shown. TABLE 7Comp. Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5Ex. 6 Ex. 7 Kind of polymer R-1 R-2 R-3 R-4 R-5 R-6 5 mol % 7 mol % 11mol % 13 mol % 17 mol % 21 mol % R-2 + R-6 Breaking 630 533 450 440 5001333 533 elongation (%) Yield strength Yield Yield Yield Yield YieldYield Yield (MPa) point point point point point point point was not wasnot was not was not was not was not was not observed observed observedobserved observed observed observed Breaking 34.0 50.0 45.0 36.0 48.07.6 34.3 strength (MPa) Elastic modulus 66.0 34.0 18.0 17.0 9.0 3.1 14.5in tension (MPa) 100% Modulus 9.0 6.0 5.0 4.0 3.0 1.3 3.8 (MPa) 300%Modulus 11.0 10.0 9.0 8.0 6.0 1.6 6.9 (MPa) Hardness 96 94 84 82 78 6382 (Shore A) Hardness 47 44 31 30 25 19 31 (Shore D) Total light 80 8582 86 Unmeasured 84 73 transmittance (%) Haze (%) 20 13 22 12 Unmeasured12 47 Vicat softening 99 94 77 70 61 40 76 point (° C.)

[0289] TABLE 8 Comparative Example 4 Example 5 Example 6 Example 7Example 8 Cross-copolymer 2-C 2-C 2-C 2-C —  100 parts  100 parts  100parts  100 parts Et-St copolymer — — — — R-3  100 parts Stabilizer  0.3part   0.3 part   0.3 part   0.3 part   0.3 part  (Irganox1010)Plasticizer — —   20 parts   50 parts — (naphthene type oil) NS-100Plasticizer —   50 parts — — — (paraffin type oil) PW-380 Poly- — — —  50 parts — propylene K-7714 Breaking 540 650 680 670 Unmeasuredelongation (%) Breaking 30 10 17 9 Unmeasured strength (MPa) Hardness 8873 79 87 Unmeasured (Shore A) C-set (%) 67 54 59 65 93

[0290] It is evident that the cross-copolymerizedstyrene/ethylene/divinylbenzene copolymers of the Examples of thepresent invention have high mechanical strengths, high melting points,Vicat Softening points and transparency. When the physical propertiesare compared with ethylene/styrene copolymers having the samecompositions (styrene contents), they show higher melting points andVicat softening points and show equivalent transparency. The meltingpoints and the Vidat softening points of the cross-copolymers of theExamples of the present invention have values substantially equal to orhigher than ethylene/styrene copolymers having the same styrene contentsas the cross chain component polymerized in the second polymerizationstep (the crossing step). Namely, cross-copolymer (1-C) obtained inExample 1 has an average styrene content of 11.6 mol %, and,nevertheless, its melting point and its vicat softening point aresubstantially equal to or higher than the ethylene/styrene copolymer(R-1 or R-2) having a styrene content of 5 or 7 mol %. Whereas, shorehardness A and D and the elastic modulus in tension are lower than R-1or R-2, which is considered to be attributable to the effects of themain chain component (the component obtained in the first polymerizationstep) having a high styrene content of the cross-copolymer.

[0291]FIG. 3 shows the relation between the styrene content and the DSCmelting point of the cross-copolymers obtained in the Examples of thepresent invention and the ethylene/styrene copolymers of the ComparativeExamples.

[0292] Further, FIG. 4 shows a relation between the styrene content andthe Vicat softening point of the cross-copolymers-obtained in theExamples of the present invention, the ethylene/styrene copolymers ofComparative Examples and the blend product obtained by mixing theethylene/styrene copolymers of Comparative Examples by a Brabender. Itis evident that the cross-copolymers of the Examples of the presentinvention have higher Vicat softening points as compared with theethylene/styrene copolymers or the blend product of the ethylene/styrenecopolymers. The blend products obtained by mixing the ethylene/styrenecopolymers of Comparative Examples by a Brabender, in FIG. 4, are ablend product of R-2 and R-6 in Table 7 (weight ratio of 1:1, averagestyrene content: 13 mol %), a blend product of R-2 and R-4 (weight ratioof 1:1, average styrene content: 11 mol %), and a blend product of R-4and R-6 (weight ratio of 1:1, average styrene content: 17 mol %).

[0293] As a Comparative Test, ethylene/styrene copolymers (R-2 and R-6)having styrene contents close to the main chain and the cross chain ofcross-copolymer (1-C) were kneaded in a weight ratio of 1:1 to obtain acomposition. The obtained composition was opaque as shown in the table.It is evident that in the case of a composition of ethylene/styrenecopolymers substantially different in their compositions (for example,different in the styrene content by at least 10 mol %), the transparencydeteriorates, as the compatibility is poor.

[0294] Further, the cross-copolymerized styrene/ethylene/dienecopolymers obtained in the Examples of the present invention show goodprocessabilities (MFR, the MFR measured under a load of 5 kg at 200° C.is at least 0.02 g/10 min.).

[0295] The gel content of the cross-copolymer was measured in accordancewith ASTM D-2765-84. Namely, accurately weighed 10 g of a polymer (amolded product having a diameter of about 1 mm and a length of about 3mm) was enclosed in a 100 mesh stainless steel net bag and accuratelyweighed. This was extracted in boiling xylene for about 5 hours,whereupon the net bag was recovered and dried under vacuum at 90° C. forat least 10 hours. After cooling sufficiently, the net bag wasaccurately weighed, and the amount of the polymer gel was calculated bythe following formula.

Gel amount=weight of polymer remaining on the net bag/weight of initialpolymer×100

[0296] The results are shown in Table 6. In each case, the gel contentwas 0% (measurable lower limit: 0.1 weight %), which shows that thecross-copolymers of the present invention have extremely low gelcontents and crosslinking degrees.

[0297] This is explained in such a way that the coordinationpolymerization catalyst used in the Examples of the present invention iscapable of copolymerizing dienes at high efficiency, and crossing willadequately proceed at a very low level of the amount of dienes used. Itis considered that the amount and the concentration of the dieneremaining in the polymerization solution are sufficiently low, wherebycrosslinking at the diene units of the copolymer during thepolymerization can be suppressed to an extremely low level, wherebyformation of the gel component will be suppressed.

[0298] Also in the crossing step, formation of the gel component issuppressed as the amount and concentration of the remaining diene arelow.

[0299] By the X-ray diffraction, a crystal structure derived fromethylene chains was confirmed with the cross-copolymers of the Examplesof the present invention i.e. polymer (1-C.), polymer (2-C) and polymer(3-C). The X-ray diffraction diagram of polymer (1-C) is shown in FIG.5. Peaks attributable to the polyethylene crystal structure are clearlyobserved in the vicinity of 2θ=21° or 24°. Amorphous scattering peaksand diffraction peaks are subjected to peak separation to obtain peakareas (peak integrated intensities), and the crystallinity was obtainedby the following formula.

Crystallinity (%)=100×(sum of integrated intensities of crystallinediffraction peaks)/(sum of integrated intensities of crystallinediffraction peaks and amorphous scattering peaks)

[0300] As a result, the crystallinity of cross-copolymer (1-C) was 30%.

[0301] As a Comparative Example, the X-ray diffraction diagram ofethylene/styrene copolymer (R-4) having substantially the same styrenecontent, is shown in FIG. 6. As compared with the cross-copolymer, thepeak intensity attributable to the polyethylene crystal structure islow, and its crystallinity was 14%.

[0302] The brittle temperatures of the cross-copolymers of the Examplesof the present invention were measured in accordance with JIS K-6723 andK-7216. As a result, cross-copolymers 1-C and 2-C both showed brittletemperatures of not higher than −60° C. A transparent soft polyvinylchloride compound (Vinikon S2100-50, manufactured by Denki Kagaku K.K.)showed a brittle temperature of substantially −25° C.

[0303]FIGS. 7 and 8 show the viscoelasticity spectra (measured at 1 Hz)of the films of the cross-copolymers obtained in Examples 1 and 2.Further, FIG. 9 shows the viscoelasticity spectrum of theethylene/styrene copolymer composition of a Comparative Example. E′(storage elastic modulus) of the cross-copolymer of the Example of thepresent invention shows a high value especially at a temperature of atleast 50° C., as compared with the ethylene/styrene copolymer having thesame styrene content. Further, E′ shows a value higher than 10⁶ Pa at100° C., and the temperature at which it lowers to 10⁶ Pa;, is about105° C., which is high as compared with about 80° C. of theethylene/styrene copolymer, thus indicating that it has high heatresistance.

[0304] It is evident that the cross-copolymer of the Example of thepresent invention has a tan δ peak component of from 0.05 to 0.8 atabout room temperature (0° C. or 25° C). Further, it has a wide range oftan δ peaks from about −30° C. to about 50° C. Specifically, the tan δvalue is at least 0.1 within a temperature range of from −10° C. to 50°C.

[0305] The copolymer of the present invention or a film made of thecopolymer of the present invention has such characteristics of E′ andtan δ value, and flexibility or softness such that hardness A is from 60to 90 and/or the elastic modulus in tension is from 10 MPa to 40 MPa.

[0306] Measurement of C-set

[0307] Using Brabender Plasti-Corder (PLE 331 model, manufactured byBrabender Company), the polymer was melted and then kneaded in a blendas shown in Table 8 at 200° C. at 60 rpm for 10 minutes to obtain asample. The sample was press-molded, and the physical properties weremeasured. Further, in accordance with JIS K6262, a high temperaturecompression permanent deformation (C-set) after heat treatment underpressure at 70° C. for 24 hours, was measured. The cross-copolymer ofthe Example of the present invention has a low C-set value (67%). Thisindicates a good-high temperature elastic recovery of thecross-copolymer of thee present invention. Further, it is also possibleto improve the C-set value and to lower the hardness, by blending itwith a plasticizer. Further, a composition with a polypropylene showedno deformation by heat treatment at 120° C. for 2 hours (a dumbbell washanged in a gear oven and the deformation was observed), and thus showedhigh heat softening resistance.

[0308] On the other hand, the C-set value of the ethylene/styrenecopolymer of the Comparative Example was 93%.

[0309] Divinylbenzene

[0310] The divinylbenzene (a mixed product of m-isomer and p-isomer)used in the following Examples 8 to 10, was manufactured by AldrichCompany (purity as divinylbenzene: 80%, a mixture of m-isomer andp-isomer, weight ratio of m-isomer:p-isomer=70:30, accordingly, theisomer purity of m-divinylbenzene is 70 weight %). In the followingpolymerization, when 1 ml (5.5 mmol as divinylbenzene) was employed per400 ml of styrene, the amount of divinylbenzene corresponds to 1/640 ofthe amount of styrene by molar ratio.

[0311] Further, in the following Examples 11 to 13, m-divinylbenzene(isomer purity: at least 97%) manufactured by Asahi Kasei Fine Chem, wasemployed. In this case, the isomers purity is the proportion ofm-divinylbenzene among o-, m- and p-divinylbenzene isomers.

EXAMPLE 8 Preparation of a Cross-copolymerizedEthylene/styrene/divinylbenzene Copolymer

[0312] Using rac-dimethylmethylenebiis (4,5-benzo-1-indenyl)zirconiumdichloride as a catalyst, the preparation was carried out, as follows.

[0313] Polymerization was carried out by means of an autoclave having acapacity of 10 l and equipped with a stirrer and a jacket for heatingand cooling.

[0314] 4400 ml of toluene, 400 ml of styrene and 2.0 ml ofdivinylbenzene manufactured by Aldrich Company were charged and heatedand stirred at an internal temperature of 70° C. About 200 l of nitrogenwas bubbled to purge the interior of the system and the polymerizationsolution. 8.4 mmol of triisobutyl aluminum and 21 mmol, based on Al, ofmethyl alumoxane (PMAO-3A, manufactured by TOSOH AKZO K.K.) were added,and ethylene was immediately introduced. After the pressure wasstabilized at 0.25 MPa (1.5 kg/cm²G), from a catalyst tank installedabove the autoclave, about 50 ml of a toluene solution having 8.4 μmolof rac-dimethylmethylenebis(4,5-benzo-1-indenyl)zirconium dichloride and0.84 mmol of triisobutyl aluminum dissolved therein, was added to theautoclave. Polymerization (the first polymerization step) was carriedout for 24 minutes while maintaining the internal temperature at 70° C.and the pressure at 0.25 MPa. At this stage, the flow volume of ethylenewas about 100 l in a standard state. At the same time as heating of thepolymerization solution was initiated, a part of the polymerizationsolution was sampled, and a polymer sample (8-A) of the firstpolymerization step was obtained by precipitation from methanol.Ethylene was introduced rapidly, and the internal pressure was broughtto 1.1 MPa in 12 minutes. In the second polymerization step, thepolymerization temperature was maintained within an internal temperaturerange of from 97° C. to 105° C. The second polymerization step wascarried out for a total of 18 minutes while maintaining the pressure at1.1 MPa.

[0315] After completion of the polymerization, the obtained polymersolution was introduced in small portions into a large amount of amethanol solution which was vigorously stirred, to recover the polymer.This polymer was dried in air at room temperature for one day, and then,dried under vacuum at 80° C. until change in weight was no longerobserved. 784 g of the polymer (8-C) was obtained.

[0316] The polymerization conditions in the respective Examples weresummarized in Table 9. The analytical results of the polymers obtainedin the respective Examples are shown in Table 10. TABLE 9 PolymerizationConditions First polymerization step (main chain polymerization step) Stconversion (%) in DVB Et Polymerization Polymerization first CatalystMAO St ml Toluene pressure temperature Et flow time polymerization Ex.μmol mmol* ml (mmol) ml MPa ° C. volume l (min.) step % Ex. 8 8.4 P; 21400 2.0 ml Note 1 4400 0.25 70 About 100 24 40 (11 mmol) Ex. 9 8.4 P;16.8 400 0.5 ml Note 1 4400 0.25 70-80 About 100 57 35 (2.8 mmol) Ex. 1021 P; 21 800 1.0 ml Note 1 4000 0.13 70 About 70 120 62 (5.5 mmol) Ex.11 8.4 P; 16.8 400 0.73 g Note 2 4400 0.25 70-80 About 150 44 53 (5.4mmol) Ex. 12 8.4 P; 16.8 400 0.73 g Note 2 4400 0.25 70-80 About 200 9165 (5.4 mmol) Ex. 13 8.4 P; 21 400 0.73 g Note 2 4400 0.25 80-85 About250 117 72 (5.4 mmol) Second polymerization step (cross chainpolymerization step) Final St Polymerization Et consumptionPolymerization conversion (%) Ex. Et pressure MPa temperature ° C.amount l time (min.) Note 3 Ex. 8 1.1 97-105 About 200 18 66 Ex. 9 1.185-102 About 300 52 60 Ex. 10 1.1 70-83  About 250 60 82 Ex. 11 1.192-104 About 270 52 79 Ex. 12 1.1 91-103 About 220 79 79 Ex. 13 1.180-95  About 170 28 89

[0317] TABLE 10 Polymerization Results Glass Heat of Styrene transitioncrystal Yield content temperature Melting fusion Ex. Polymers 1) g mol %Mw/10⁴ Mw/Mn ° C. point ° C. J/g Ex. 8 8-A 286 22.1 17.8 2.5 −20  42  48-B 498 5.8 — — — — — 8-C 784 10.6 (17.4) (2.9) −21  97 57 Ex. 9 9-A 25021.3 15.5 2.2 −19  44  5 9-B 635 4.5 — — — — — 9-C 885 8.2 UnmeasurableUnmeasurable −19 105 63 Ex. 10 10-A 610 42.9 14.9 2.4   17   92*  19*10-B 623 7.7 — — — — — 10-C 1233 20.1 (12.7) (2.5) −23, −16  80 30 Ex.11 11-A 405 19.6 17.3 2.5 −19  47  8 11-B 565 5.1 — — — — — 11-C 97010.2 Unmeasurable Unmeasurable −20 103 58 Ex. 12 12-A 530 17.8 20.2 2.8−20  51 10 12-B 447 3.4 — — — — — 12-C 977 10.1 UnmeasurableUnmeasurable −21 109 53 Ex. 13 13-A 651 15.4 17.3 2.8 −22  60 11 13-B326 6.2 — — — — — 13-C 977 11.9 Unmeasurable Unmeasurable −21 112 49

[0318] In Table 10, in addition to the polymer (such as 8-A) obtained inthe first polymerization step and the cross-copolymer i.e. the polymer(such as 8-C) finally obtained through the second polymerization step,the weight and the composition of the polymer (such as 8-B) polymerizedin the second polymerization step are also shown as determined fromweight balance.

EXAMPLES 9 and 10

[0319] Under the conditions shown in Table 9, polymerization and posttreatment were carried out in the same manner as in Example 8.

EXAMPLES 11 TO 13

[0320] Under the conditions shown in Table 9, polymerization and posttreatment were carried out in the same manner as in Example 8. However,the divinylbenzene employed was m-divinylbenzene (isomer purity: atleast 97%) manufactured by Asahi Kasei Fine Chem.

[0321] The cross copolymerization conditions in these Examples satisfythe preferred conditions for obtaining cross-copolymers having goodmoldability, as follows.

[0322] Example 8 satisfies a condition that a) in the first and/orsecond polymerization step, the polymerization temperature issubstantially always at least 80° C., preferably at least 85° C. and atmost 160° C. during the polymerization.

[0323] Example 9 satisfies a condition that a) in the first and/orsecond polymerization step, the polymerization temperature issubstantially always at least 80° C., preferably at least 85° C. and atmost 160° C., during the polymerization.

[0324] Example 10 satisfies a condition that b) the aromatic vinylcompound content of the polymer obtained in the first polymerizationstep is at least 30 mol %, and its weight average molecular weight is atmost 250,000.

[0325] Examples 11 to 13 satisfy conditions that a) in the first and/orsecond polymerization step, the polymerization temperature issubstantially always at least 80° C., preferably at least 85° C. and atmost 160° C., during the polymerization, and c) the diene to be employedis m-divinylbenzene having an isomer purity of at least 80 weight %,preferably at least 90 weight %.

[0326] By the gas chromatography analysis of the polymerization solutionwithdrawn upon completion of the first polymerization step, the amountof divinylbenzene remaining in the polymerization solution was obtained,and the amount of divinylbenzene consumed in the first polymerizationstep was obtained. From the value, the obtained in each Example and theisotactic diad index m of the styrene unit/ethylene unit alternatingstructure, were obtained in accordance with the above formulae (i) and(ii), respectively. λ values of 8-A, 9-A, 11-A, 12-A and 13-A obtainedin the first polymerization step were within a range of from 12 to 20,and λ value of 10-A was 39.

[0327] λ values of the cross-copolymers 8-C, 9-C, 11-C, 12-C and 13-Cobtained through the second polymerization step were within a range offrom 7 to 15, and λ value of 10-C was 24.

[0328] m value of each polymer was at least 0.95. The result ofmeasurement of physical properties of the obtained polymers are shown inTable 11. TABLE 11 Example 8 Example 9 Example 11 Example 12 Example 13Kind of 8-C 9-C 11-C 12-C 13-C polymer Breaking 510 633 483 443 520elongation (%) Yield strength Yield point Yield point Yield point Yieldpoint Yield point (MPa) was not was not was not was not was not observedobserved observed observed observed Breaking 26.1 20.9 25.0 22.7 27.0strength (MPa) Elastic 20.2 35.0 24.2 29.1 17.2 modulus in tension (MPa)100% modulus 5.0 6.0 5.2 5.7 4.0 (MPa) 300% modulus 8.9 7.4 9.4 9.4 8.6(MPa) Hardness 90 95 88 88 84 (Shore A) Hardness 35 42 37 37 32 (ShoreD) Total light 81 73 83 85 83 transmittance (%) Haze (%) 11 18 11 11 12

[0329] It is evident that the cross-copolymerizedstyrene/ethylene/divinylbenzene copolymers of the Examples of thepresent invention have high mechanical strengths, high melting pointsand transparency. When the physical properties are compared withethylene/styrene copolymers having the same compositions (styrenecontents), they show higher melting points and show transparencyequivalent to or higher than the ethylene/styrene copolymers. Themelting points of the cross-copolymers of the Examples of the presentinvention have values substantially equal to or higher thanethylene/styrene copolymers having the same styrene contents as thecross chain component polymerized in the second polymerization step (thecrossing step). Namely, cross-copolymer (8-C). obtained in Example 8 hasan average styrene content of 10.6 mol %, and, nevertheless, its meltingpoint is significantly higher than the ethylene/styrene copolymer havingthe same styrene content. Whereas, shore hardness A and D and theelastic modulus in tension of the cross-copolymer are substantially thesame as the ethylene/styrene copolymer having the same styrene content,thus showing that the cross-copolymer has both heat resistance andsoftness. This is considered to be attributable to the effects of themain chain component (the component obtained in the first polymerizationstep) having a high styrene content and low crystallinity and the crosschain component (the component obtained in the second polymerizationstep) having a low styrene content and high crystallinity.

[0330]FIG. 9 shows the relation between the styrene content and the DSCmelting point of the cross-copolymers obtained in Examples 8 to 13 ofthe present invention and the ethylene/styrene copolymers of theComparative Examples.

[0331] The cross-copolymerized styrene/ethylene/diene copolymersobtained in Examples of the present invention, show good processability(ER; i.e. MFR as measured under a load of 5 kg at 230° C. being at least1.0 g/10 min and at most 50 g/10 min) (Table 12)

[0332] In general, there is a tendency that the processability (MFR)decreases as the final conversion of styrene (the conversion of thearomatic vinyl compound monomer species throughout all polymerizationsteps) increases. Such a decrease in the mold processability is observedparticularly distinctly in a case where the aromatic vinyl compoundcontent of the polymer obtained in the first polymerization step is lessthan 30 mol %. However, especially in a case whereas a diene,m-divinylbenzene having an isomer purity of at least 80 weight %,preferably at least 90 weight % (Examples 11, 12 and 13) is used, evenif a cross-copolymer is produced under such a condition that the finalconversion of styrene (an aromatic vinyl compound) is at least 70%, theobtainable cross-copolymer has a characteristic of showing goodprocessability (MFR, i.e. MFR as measured under a load of 5 kg at 230°C. being at least 1.0 g/10 min. and at most 50 g/10 min.). It ispreferred to employ m-divinylbenzene for the production of across-copolymer from such a viewpoint that good mold processability (M)is obtainable while maintaining various physical properties such as heatresistance and transparency even under such a condition. TABLE 12 MFREx. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 (g/10 min.) 8-C 9-C 10-C 11-C12-C 13-C 230° C., load 1.5 2.3 1.9 1.2 1.2 1.1 5 kg 230° C., load 6.78.8 5.9 5.2 6.0 4.0 10 kg

[0333] The gel contents of the cross-copolymers obtained in Examples 8to 13 were measured in accordance with ASTM D-2765-84. In thecross-copolymers in all of such Examples, the gel content was 0 weight %(the lower limit for measurement: 0.1 weight %), whereby it is evidentthat the cross-copolymers of the present invention have extremely lowgel contents or crosslinking degrees.

[0334] By the X-ray diffraction, a crystal structure derived fromethylene chains was confirmed with the cross-copolymers of Examples 8 to13 of the present invention.

[0335] The brittle temperatures of the cross-copolymers in Examples ofthe present invention were measured in accordance with JIS K-6723 andK-7216 As a result, each of cross-copolymers 8-C, 9-C, 11-C, 12-C and13-C, showed a brittle temperature of not higher than −60° C.

[0336]FIG. 11 shows a transmission, electron microscopic (TEM)photograph of the cross-copolymer obtained in Example 8 and FIG. 12shows a TEM photograph of the ethylene/styrene copolymer composition ofComparative Example 7.

[0337] In the case of the ethylene/styrene copolymer composition,copolymer portions (white portions) having a low styrene content andcopolymer portions (black portions) having a relatively high styrenecontent are phase-separated in sizes of a few microns, and iscrystalline lamella (white needle crystal) is present only inside of thecopolymer regions having a low styrene content. This result indicateslow compatibility of ethylene/styrene copolymers having differentcompositions from each other.

[0338] Whereas, in the cross-copolymer, the portions (white portions)having a low styrene content and the portions (black portions) having arelatively high styrene content are both finely distributed in sizes ofabout 0.1 μm or smaller. Further, crystalline lamella (white needlecrystal) is present substantially at the interface, and it is alsoobserved in high styrene regions, and thus it takes a specific structurebridging both phases.

EXAMPLES 14 TO 19 AND COMPARATIVE EXAMPLE 9

[0339] In accordance with the blend ratios shown in Table 13, copolymercompositions were obtained, and by the following method, C-set and heatresistance were measured.

[0340] Measurement of C-set

[0341] Using Brabender Plasti-Corder (PLE 331 model, manufactured byBrabender Company), the polymer was melted and then kneaded in a blendratio as shown in Table 13 at 200° C. at 60 rpm for 10 minutes to obtaina sample. The sample was press-molded, and the physical properties weremeasured. Further, in accordance with JIS K6262, a high temperaturecompression permanent deformation (C-set) after heat treatment underpressure at 70° C. for 24 hours, was measured (Table 13). The heatresistance was evaluated by heat treatment of a dumbbell obtained bypress molding (the dumbbell was hanged in a gear oven at 120° C. for twohours, and the deformation was observed).

[0342] The cross-copolymers of Examples of the present invention havelow C-set values (65%). This indicates a good elastic recovery under ahigh temperature condition of the cross-copolymers of the presentinvention. Further, the heat resistance is also relatively good.Further, it is possible to improve the C-set value or to lower thehardness by blending the copolymer with a plasticizer.

[0343] On the other hand, the C-set value of the composition(Comparative Example 9) comprising ethylene/styrene copolymers havingdifferent compositions, is poor at 100%, and the heat resistance is alsopoor.

[0344] The composition comprising the cross-copolymer, a polyolefin(polyethylene) and a plasticizer showed a good C-set value and high heatresistance (Examples 18 and 19). TABLE 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17Ex. 18 Ex. 19 Comp. Ex. 9 Blend Cross-copolymer 8-C 9-C 11-C 12-C 12-C12-C — ratio  100 parts  100 parts  100 parts  100 parts  100 parts  100parts Et-St copolymer — — — — R-1:50 parts + R-6:50 parts High density —— — —   50 parts   20 parts — polyethylene 7000 F Plasticizer NS-100 — —— —   50 parts   50 parts — (Naphthene type oil) Physical Breaking — — —— 780 720 — property elongation (%) Breaking strength — — — — 12.6 10.0— (MPa) Hardness (Shore A) — — — — 93 87 — Stabilizer  0.3 part   0.3part   0.3 part   0.3 part   0.3 part   0.3 part   0.3 part  (Irganox1010) C-set (%) 69 65 65 68 49 53 100 Heat resistance ◯ ◯ ◯ ◯ ⊚ ⊚ X(120° C., 2 hours)

[0345] Industrial Applicability

[0346] According to the present invention, a cross-copolymerizedolefin/styrene/diene copolymer excellent in mechanical properties, hightemperature characteristics, compatibility and transparency, andindustrially excellent processes for the production of such across-copolymer and its composition, are presented.

[0347] The entire disclosures of Japanese Patent Application No.11-258618 filed on Sep. 13, 1999, Japanese Patent Application No.2000-184053 filed on Jun. 20, 2000, Japanese Patent Application No.2001-044715 filed on Feb. 21, 2001, and Japanese Patent Application No.2001-221247 filed on Jul. 23, 2001 including specifications, claims,drawings and summaries are incorporated herein by reference in theirentireties.

1. A cross-copolymerized olefin/aromatic vinyl compound/diene copolymercharacterized in that it is obtained by cross-copolymerizing anolefin/aromatic vinyl compound/diene copolymer having an aromatic vinylcompound content of from 0.03 mol % to 96 mol %, a diene content of from0.0001 mol % to 3 mol % and the rest being an olefin, with anolefin/aromatic vinyl compound copolymer (which may contain a diene)having an aromatic vinyl compound content which is different by at least5 mol %.
 2. A cross-copolymerized olefin/aromatic vinyl compound/dienecopolymer characterized in that it is obtained by using anolefin/aromatic vinyl compound/diene copolymer having an aromatic vinylcompound content of from 0.03 mol % to 96 mol %, a diene content of from0.0001 mol % to 3 mol % and the rest being an olefin, andcross-copolymerizing it, wherein the aromatic vinyl compound content isdifferent by at least 2 mol % as compared with the olefin/aromatic vinylcompound/diene copolymer prior to the cross-copolymerization.
 3. Thecross-copolymerized olefin/aromatic vinyl compound/diene copolymeraccording to claim 2, characterized in that it has an aromatic vinylcompound content of from 5 mol % to 50 mol %, a diene content of from0.0001 mol % to 3 mol % and the rest being ethylene or at least twotypes of olefins including ethylene, and it has a crystal structurederived from an ethylene chain structure, wherein the aromatic vinylcompound content and at least one of the melting point such that theheat of crystal fusion as measured by DSC is at least 10 J/g and at most150 J/g, satisfies the following relation:(5≦St≦15)−3·St+125≦Tm≦140(15<St≦50)80<Tm≦140) where Tm is the meltingpoint (° C.) such that the heat of crystal fusion is at least 10 J/g andat most 150 J/g, and St is the aromatic vinyl compound content (mol %).4. A process for producing a cross-polymerized olefin/aromatic vinylcompound/diene copolymer, characterized in that the production iscarried out by employing a polymerization process of at least two stepscomprising, as a first polymerization step (main chain polymerizationstep), carrying out copolymerization of an aromatic vinyl compoundmonomer, an olefin monomer and a diene monomer by means of acoordination polymerization catalyst to synthesize an olefin/aromaticvinyl compound/diene copolymer, and then, as a second polymerizationstep (crossing step) under conditions different therefrom, carrying outpolymerization in the coexistence of this olefin/aromatic vinylcompound/diene copolymer and at least an olefin and an aromatic vinylcompound monomer by means of a coordination polymerization catalyst. 5.The process according to claim 4, wherein the amount of the diene usedin the first polymerization step is from 1/50000 to 1/100 (molar ratio)of the amount of the aromatic vinyl compound monomer.
 6. The processaccording to claim 4, wherein the polymerization solution obtained bythe first polymerization step is used for a polymerization step of thesecond or subsequent polymerization step without separation and recoveryof the olefin/aromatic vinyl compound/diene copolymer.
 7. Across-copolymerized olefin/aromatic compound/diene copolymer having anaromatic vinyl compound content of from 0.03 mol % to 96 mol %, a dienecontent of from 0.0001 mol % to 3 mol % and the rest being an olefinobtained by the process as defined in claim
 4. 8. Thecross-copolymerized olefin/aromatic compound/diene copolymer accordingto claim 2 or 7, characterized in that the olefin is ethylene or atleast two types of olefins including ethylene.
 9. Thecross-copolymerized olefin/aromatic compound/diene copolymer accordingto claim 2 or 7, characterized in that the aromatic vinyl compound isstyrene.
 10. The cross-copolymerized olefin/aromatic compound/dienecopolymer according to claim 2 or 7, characterized in that the diene isat least one of o-divinylbenzene, p-divinylbenzene and m-divinylbenzene.11. The cross-copolymerized olefin/aromatic compound/diene copolymeraccording to claim 2 or 7, wherein the diene is m-divinylbenzene havingan isomer purity of at least 80 weight %.
 12. The cross-copolymerizedolefin/aromatic compound/diene copolymer according to claim 2 or 7,characterized in that MFR as measured under a load of 5 kg at 200° C. isat least 0.02 g/10 min. and at most 100 g/10 min., or MFR as measuredunder a load of 5 kg at 230° C. is at least 1.0 g/min. and at mqst 50g/10 min.
 13. The cross-copolymerized olefin/aromatic compound/dienecopolymer according to claim 2 or 7, characterized in that the gelcontent is less than 10 weight %.
 14. The cross-copolymerizedolefin/aromatic compound/diene copolymer according to claim 2 or 7,characterized in that in a molded product of 1 mm in thickness, it has atotal light transmittance of at least 75% and/or a haze of at most 30%.15. The process according to claim 4, characterized in that thecoordination polymerization catalyst to be used in the firstpolymerization step and the second polymerization step is a single sitecoordination polymerization catalyst.
 16. The process according to claim4, characterized in that the coordination polymerization catalyst to beused in the first polymerization step and the second polymerization stepis a single site coordination polymerization catalyst comprising atransition metal compound represented by the following general formula(1) and a cocatalyst:

wherein A and B are independently a group selected from an unsubstitutedor substituted benzoindenyl group, an unsubstituted or substitutedcyclopentadienyl group, an unsubstituted or substituted indenyl group,or an unsubstituted or substituted fluorenyl group; Y is a methylenegroup, a silylene group, an ethylene group, a germilene group or a boronresidue, which has bonds to A and B and which further has hydrogen or agroup containing a C₁₋₂₀ hydrocarbon (this group may have from 1 to 3nitrogen, boron, silicon, phosphorus, selenium, oxygen or sulfur atoms),as a substituent, the substituents may be the same or different from oneanother, and Y may have a cyclic structure such as a cyclohexylidenegroup or a cyclopentylidene group; each X is independently hydrogen, ahalogen, a C₁₋₁₅ alkyl group, a C₆₋₁₀ aryl group, a C₈₋₁₂ alkylarylgroup, a silyl group having a C₁₋₄ hydrocarbon substituent, a C₁₋₁₀alkoxy group, or an amide group having hydrogen or a C₁₋₂₂ hydrocarbonsubstituent, and n is an integer of 0, 1 or 2; and M is zirconium,hafnium or titanium.
 17. The process according to claim 16,characterized in that at least one of A and B in the general formula (1)is an unsubstituted or substituted benzoindenyl group, or anunsubstituted or substituted indenyl group.
 18. A molded productobtained by molding the cross-copolymerized olefin/aromatic vinylcompound/diene copolymer as defined in claim 2 or
 7. 19. A film made ofthe cross-copolymerized olefin/aromatic vinyl compound/diene copolymeras defined in claim 2 or
 7. 20. A composition characterized in that itcontains from 1 to 99 weight % of the cross-copolymerizedolefin/aromatic vinyl compound/diene copolymer as defined in claim 2 or7.
 21. A molded product obtained by molding a composition which containsfrom 1 to 99 weight % of the cross-copolymerized olefin/aromatic vinylcompound/diene copolymer as defined in claim 2 or
 7. 22. A compositioncomprising the cross-copolymerized olefin/aromatic vinyl compound/dienecopolymer as defined in claim 2 or 7, and a polyolefin, and/or aplasticizer.
 23. An olefin/aromatic vinyl compound/divinylbenzenecopolymer having an aromatic vinyl compound content of from 0 mol % to96 mol %, a diene content of from 0.0001 mol % to 3 mol % and the restbeing an olefin, obtained by copolymerizing m-divinylbenzene having anisomer purity of at least 80 weight %, an olefin and an aromatic vinylcompound.